Question: what is known about those infected with Covid-19 but are asymptomatic?

Title: There are asymptomatic and pre-symptomatic patients infected with COVID-19. So what? Pandemic response implications Content: Abstract Asymptomatic but infectious people have been reported in many infectious diseases. Asymptomatic and pre-symptomatic carriers would be a hidden reservoir of COVID-19. Aim This review identifies primary empirical evidence about the ability of asymptomatic carriers to infect others with COVID-19 pandemic and reflects on the implications for control measures. Methods A systematic review is followed by a narrative report and commentary inclusion criteria were: studies reporting primary data on asymptomatic or pre-symptomatic patients, who were considered to have passed on COVID-19 infection; and published in indexed journals or in peer review between January 1 and March 31, 2020. Results Nine articles reported on 83 asymptomatic or pre-symptomatic persons. Conclusions The evidence confirms COVID-19 transmission from people who were asymptomatic at the time. A series of implications for health service response are laid out. Keywords: Covid-19, Asymptomatic, Pre-symptomatic, Public Health

Title: Characteristics of asymptomatic patients with SARS-CoV-2 infection in Jinan, China Content: Coronavirus Disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2(SARS-CoV-2) is continuously and rapidly circulating at present. Asymptomatic patients have been proven to be contagious and thus pose a significant infection control challenge. Here we describe the characteristics of asymptomatic patients with SARS-CoV-2 infection in Jinan, Shandong province, China. A total of 47 patients with confirmed COVID-19 were recruited. Among them, 11 patients were categorized as asymptomatic cases. We found that the asymptomatic patients in Jinan were relatively young and were mainly clustered cases. The laboratory indicators and lung lesion on chest CT were mild. No special factors were found accounting for the presence or absence of symptoms. The presence of asymptomatic patients increased the difficulty of screening. It is necessary to strengthen the identification of such patients in the future.

Title: Otolaryngology Providers Must Be Alert for Patients with Mild and Asymptomatic COVID-19 Content: More than half of COVID-19 patients are afebrile early in the disease course, yet mildly ill or asymptomatic patients can still spread SARS-CoV-2 with high efficiency. Atypically presenting patients may be seen in noninfectious disease settings such as otolaryngology, which is a specialty prone to occupational exposure. Otolaryngologists have been infected with COVID-19 at higher rates than other specialties in China and other countries. Otolaryngology providers should maintain high clinical suspicion for mild and asymptomatic COVID-19 patients. Protective strategies should be implemented including preappointment screening, triaging, restriction of nonurgent visits and surgeries, telemedicine, and appropriate personal protective equipment use.

Title: Otolaryngology Providers Must Be Alert for Patients with Mild and Asymptomatic COVID-19. Content: More than half of COVID-19 patients are afebrile early in the disease course, yet mildly ill or asymptomatic patients can still spread SARS-CoV-2 with high efficiency. Atypically presenting patients may be seen in noninfectious disease settings such as otolaryngology, which is a specialty prone to occupational exposure. Otolaryngologists have been infected with COVID-19 at higher rates than other specialties in China and other countries. Otolaryngology providers should maintain high clinical suspicion for mild and asymptomatic COVID-19 patients. Protective strategies should be implemented including preappointment screening, triaging, restriction of nonurgent visits and surgeries, telemedicine, and appropriate personal protective equipment use.

Title: Characteristics of asymptomatic patients with SARS-CoV-2 infection in Jinan, China Content: Abstract Coronavirus Disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2(SARS-CoV-2) is continuously and rapidly circulating at present. Asymptomatic patients have been proven to be contagious and thus pose a significant infection control challenge. Here we describe the characteristics of asymptomatic patients with SARS-CoV-2 infection in Jinan, Shandong province, China. A total of 47 patients with confirmed COVID-19 were recruited. Among them, 11 patients were categorized as asymptomatic cases. We found that the asymptomatic patients in Jinan were relatively young and were mainly clustered cases. The laboratory indicators and lung lesion on chest CT were mild. No special factors were found accounting for the presence or absence of symptoms. The presence of asymptomatic patients increased the difficulty of screening. It is necessary to strengthen the identification of such patients in the future.

Title: A systematic review of asymptomatic infections with COVID-19 Content: Since the outbreak of coronavirus disease 2019 (COVID-19) in late December 2019, it has brought significant harm and challenges to over 200 countries and regions around the world. However, there is increasing evidence that many patients with COVID-19 are asymptomatic or have only mild symptoms, but they are able to transmit the virus to others. There are difficulties in screening for asymptomatic infections, which makes it more difficult for national prevention and control of this epidemic. This article reviews the characteristics, treatment, and outcomes of asymptomatic infections with COVID-19, hoping it would be helpful for early prevention and control of this severe public health threat worldwide.

Title: A Systematic Review of Asymptomatic Infections with COVID-19 Content: Since the outbreak of coronavirus disease 2019 (COVID-19) in late December 2019, it has brought significant harm and challenges to over 200 countries and regions around the world. However, there is increasing evidence that many patients with COVID-19 are asymptomatic or have only mild symptoms, but they are able to transmit the virus to others. There are difficulties in screening for asymptomatic infections, which makes it more difficult for national prevention and control of this epidemic. This article reviews the characteristics, treatment, and outcomes of asymptomatic infections with COVID-19, hoping it would be helpful for early prevention and control of this severe public health threat worldwide.

Title: Delivery of infection from asymptomatic carriers of COVID-19 in a familial cluster Content: OBJECTIVES: With the ongoing outbreak of COVID-19 around the world, it has become a worldwide health concern. One previous study reported a family cluster with an asymptomatic transmission of COVID-19. Here, we report another series of cases and further demonstrate the repeatability of the transmission of COVID-19 by pre-symptomatic carriers. METHODS: A familial cluster of five patients associated with COVID-19 was enrolled in the hospital. We collected epidemiological and clinical characteristics, laboratory outcomes from electronic medical records, and also verified them with the patients and their families. RESULTS: Among them, three family members (Case 3/4/5) had returned from Wuhan. Additionally, two family members, those who had not traveled to Wuhan, also contracted COVID-19 after contacting with the other three family members. Case 1 developed severe pneumonia and was admitted to the ICU. Case 3 and Case 5 presented fever and cough on days two through three of hospitalization and had ground-glass opacity changes in their lungs. Case 4 presented with diarrhea and pharyngalgia after admission without radiographic abnormalities. Case 2 presented no clinical nor radiographic abnormalities. All five cases had an increasing level of C-reactive protein. CONCLUSIONS: Our findings indicate that COVID-19 can be transmitted by asymptomatic carriers during the incubation period.

Title: A study on infectivity of asymptomatic SARS-CoV-2 carriers Content: BACKGROUND: An ongoing outbreak of coronavirus disease 2019 (COVID-19) has spread around the world. It is debatable whether asymptomatic COVID-19 virus carriers are contagious. We report here a case of the asymptomatic patient and present clinical characteristics of 455 contacts, which aims to study the infectivity of asymptomatic carriers. MATERIAL AND METHODS: 455 contacts who were exposed to the asymptomatic COVID-19 virus carrier became the subjects of our research. They were divided into three groups: 35 patients, 196 family members and 224 hospital staffs. We extracted their epidemiological information, clinical records, auxiliary examination results and therapeutic schedules. RESULTS: The median contact time for patients was four days and that for family members was five days. Cardiovascular disease accounted for 25% among original diseases of patients. Apart from hospital staffs, both patients and family members were isolated medically. During the quarantine, seven patients plus one family member appeared new respiratory symptoms, where fever was the most common one. The blood counts in most contacts were within a normal range. All CT images showed no sign of COVID-19 infection. No severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections was detected in 455 contacts by nucleic acid test. CONCLUSION: In summary, all the 455 contacts were excluded from SARS-CoV-2 infection and we conclude that the infectivity of some asymptomatic SARS-CoV-2 carriers might be weak.

Title: Prevalence of Asymptomatic SARS-CoV-2 Infection: A Narrative Review Content: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread rapidly throughout the world since the first cases of coronavirus disease 2019 (COVID-19) were observed in December 2019 in Wuhan, China. It has been suspected that infected persons who remain asymptomatic play a significant role in the ongoing pandemic, but their relative number and effect have been uncertain. The authors sought to review and synthesize the available evidence on asymptomatic SARS-CoV-2 infection. Asymptomatic persons seem to account for approximately 40% to 45% of SARS-CoV-2 infections, and they can transmit the virus to others for an extended period, perhaps longer than 14 days. Asymptomatic infection may be associated with subclinical lung abnormalities, as detected by computed tomography. Because of the high risk for silent spread by asymptomatic persons, it is imperative that testing programs include those without symptoms. To supplement conventional diagnostic testing, which is constrained by capacity, cost, and its one-off nature, innovative tactics for public health surveillance, such as crowdsourcing digital wearable data and monitoring sewage sludge, might be helpful.

Title: Challenges of managing the asymptomatic carriers of SARS-CoV-2 Content: After an outbreak in Wuhan, China, a growing number of countries are now suffering from an epidemic by SARS-CoV-2, which causes COVID-19. Undoubtedly, reports of the skyrocketing global spread of COVID-19 has shocked people globally, from Japan to the United States. Presently, the World Health Organization indicates that the fatality rate due to COVID-19 is about 2%, inferring that many positive subjects may potentially overcome the illness with mild influenza-like symptoms and no need for hospitalization at intensive-care units. Because COVID-19 is completely new to the human immune system, many throughout the world are likely vulnerable to becoming sick after their initial exposure to SARS-CoV-2. Besides hospitalized cases, many individuals are likely asymptomatic but potentially carry the virus. While our knowledge about carriers and their virus shedding is deficient, some studies modelling the viral transmission have considered the potential contribution of the asymptomatic carriers. Protocols for managing asymptomatic cases, for example for controlling them to restrict their contact with healthy people at public places or private residences, have not been established. In-house quarantine may as well be applicable to asymptomatic cases if they could be identified and diagnosed. Presumably now, the asymptomatic subjects potentially contribute to the transmission of COVID-19 without their knowledge, intention, or being diagnosed as carriers. Thus, managing the asymptomatic subjects, who can carry and likely transmit the virus, is a major healthcare challenge while the pandemic is looming.

Title: Characterization of an asymptomatic cohort of SARS-COV-2 infected individuals outside of Wuhan, China Content: BACKGROUND: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2, resulting in the coronavirus disease COVID-19) is highly transmissible among people. Asymptomatic infections are also an important source of infection. Here, we aimed to further clarify the epidemiologic and clinical characteristics of asymptomatic SARS-CoV-2 infections. METHODS: We identified close contacts of confirmed COVID-19 cases in northeast Chongqing who were RT-PCR+ yet remained asymptomatic throughout their infections. We stratified this cohort by normal versus abnormal findings on chest CT, and compared the strata regarding comorbidities, demographics, laboratory findings, viral transmission and other factors. RESULTS: Between January and March, 2020, we identified and hospitalized 279 RT-PCR+ contacts of COVID-19 patients. Of these, 63 (23%) remained asymptomatic until discharge; 29 had abnormal and 34 had normal chest CT findings. The mean cohort age was 39.3 years, and 87.3% had no comorbidities. Mean time to diagnosis after close contact with a COVID-19 index patient was 16.0 days (range 1 to 29), and 13.4 days and 18.7 days for those with abnormal and normal CT findings, respectively (p < 0.05). Nine subjects (14.3%) transmitted the virus to others; 4 and 5 were in the abnormal and normal CT strata, respectively. The median length of nucleic acid turning negative in asymptomatic COVID-19 patients was 13 days, compared to 10.4 days in those with normal chest CT (p < 0.05). CONCLUSIONS: A portion of these asymptomatic individuals, with and without abnormal chest CT scans, were capable of transmitting the virus to others. Given the frequency and potential infectiousness of asymptomatic infections, testing of traced contacts is essential. Studies of the impact of treatment on asymptomatic RT-PCR+ individuals on disease progression and transmission should be undertaken.

Title: Clinical characteristics of 24 asymptomatic infections with COVID-19 screened among close contacts in Nanjing, China Content: Previous studies have showed clinical characteristics of patients with the 2019 novel coronavirus disease (COVID-19) and the evidence of person-to-person transmission. Limited data are available for asymptomatic infections. This study aims to present the clinical characteristics of 24 cases with asymptomatic infection screened from close contacts and to show the transmission potential of asymptomatic COVID-19 virus carriers. Epidemiological investigations were conducted among all close contacts of COVID-19 patients (or suspected patients) in Nanjing, Jiangsu Province, China, from Jan 28 to Feb 9, 2020, both in clinic and in community. Asymptomatic carriers were laboratory-confirmed positive for the COVID-19 virus by testing the nucleic acid of the pharyngeal swab samples. Their clinical records, laboratory assessments, and chest CT scans were reviewed. As a result, none of the 24 asymptomatic cases presented any obvious symptoms while nucleic acid screening. Five cases (20.8%) developed symptoms (fever, cough, fatigue, etc.) during hospitalization. Twelve (50.0%) cases showed typical CT images of ground-glass chest and 5 (20.8%) presented stripe shadowing in the lungs. The remaining 7 (29.2%) cases showed normal CT image and had no symptoms during hospitalization. These 7 cases were younger (median age: 14.0 years; P=0.012) than the rest. None of the 24 cases developed severe COVID-19 pneumonia or died. The median communicable period, defined as the interval from the first day of positive nucleic acid tests to the first day of continuous negative tests, was 9.5 days (up to 21 days among the 24 asymptomatic cases). Through epidemiological investigation, we observed a typical asymptomatic transmission to the cohabiting family members, which even caused severe COVID-19 pneumonia. Overall, the asymptomatic carriers identified from close contacts were prone to be mildly ill during hospitalization. However, the communicable period could be up to three weeks and the communicated patients could develop severe illness. These results highlighted the importance of close contact tracing and longitudinally surveillance via virus nucleic acid tests. Further isolation recommendation and continuous nucleic acid tests may also be recommended to the patients discharged. ELECTRONIC SUPPLEMENTARY MATERIAL: Supplementary material is available for this article at 10.1007/s11427-020-1661-4 and is accessible for authorized users.

Title: A study on infectivity of asymptomatic SARS-CoV-2 carriers. Content: BACKGROUND An ongoing outbreak of coronavirus disease 2019 (COVID-19) has spread around the world. It is debatable whether asymptomatic COVID-19 virus carriers are contagious. We report here a case of the asymptomatic patient and present clinical characteristics of 455 contacts, which aims to study the infectivity of asymptomatic carriers. MATERIAL AND METHODS 455 contacts who were exposed to the asymptomatic COVID-19 virus carrier became the subjects of our research. They were divided into three groups: 35 patients, 196 family members and 224 hospital staffs. We extracted their epidemiological information, clinical records, auxiliary examination results and therapeutic schedules. RESULTS The median contact time for patients was four days and that for family members was five days. Cardiovascular disease accounted for 25% among original diseases of patients. Apart from hospital staffs, both patients and family members were isolated medically. During the quarantine, seven patients plus one family member appeared new respiratory symptoms, where fever was the most common one. The blood counts in most contacts were within a normal range. All CT images showed no sign of COVID-19 infection. No severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections was detected in 455 contacts by nucleic acid test. CONCLUSION In summary, all the 455 contacts were excluded from SARS-CoV-2 infection and we conclude that the infectivity of some asymptomatic SARS-CoV-2 carriers might be weak.

Title: Delivery of infection from asymptomatic carriers of COVID-19 in a familial cluster Content: Abstract Objectives With the ongoing outbreak of COVID-19 around the world, it has become a worldwide health concern. One previous study reported a family cluster with asymptomatic transmission of COVID-19. Here, we report another series of cases and further demonstrate the repeatability of the transmission of COVID-19 by pre-symptomatic carriers. Methods A familial cluster of five patients associated with COVID-19 was enrolled in the hospital. We collected epidemiological and clinical characteristics, laboratory outcomes from electronic medical records, and also affirmed them with the patients and their families. Results Among them, three family members (Case 3/4/5) had returned from Wuhan. Additionally, two family members, those who had not travelled to Wuhan, also contracted COVID-19 after contacting with the other three family members. Case 1 developed severe pneumonia and was admitted to the ICU. Case 3 and Case 5 presented fever and cough on days 2 through 3 of hospitalization and had ground-glass opacity changes in their lungs. Case 4 presented with diarrhoea and pharyngalgia after admission without radiographic abnormalities. Case 2 presented no clinical or radiographic abnormalities. All the cases had an increasing level of C-reactive protein. Conclusions Our findings indicate that COVID-19 can be transmitted by asymptomatic carriers during the incubation period.

Title: Clinical characteristics of asymptomatic and symptomatic patients with mild COVID-19 Content: OBJECTIVES: Detailed knowledge on the prevalence of asymptomatic cases of coronavirus disease 2019 (COVID-19) and the clinical characteristics of mild COVID-19 is essential for effective control of the COVID-19 pandemic. We determined the prevalence of asymptomatic cases of COVID-19 and characterized the symptoms of patients with mild COVID-19. METHODS: Study participants were recruited from a community facility designated for the isolation of patients without moderate-to-severe symptoms of COVID-19 in South Korea. The prevalence of asymptomatic patients at admission and the detailed symptoms of mild COVID-19 were evaluated through a questionnaire-based survey. Diagnosis of COVID-19 was confirmed by real-time RT-PCR. RESULTS: Of the 213 individuals with COVID-19, 41 (19.2%) were asymptomatic until admission. Among the remaining patients with mild COVID-19, the most common symptom was cough (40.1%; 69/172), followed by hyposmia (39.5%; 68/172) and sputum (39.5%; 68/172). Of the 68 individuals with hyposmia, 61 (90%) had accompanying symptoms such as hypogeusia, nasal congestion or rhinorrhoea. Fever (>37.5°C) was only observed in 20 (11.6%) individuals. CONCLUSIONS: As much as one-fifth of individuals with COVID-19 remained asymptomatic from exposure to admission. Hyposmia was quite frequent among individuals with mild COVID-19, but fever was not. Social distancing should be strongly implemented to prevent disease transmission from asymptomatic individuals or those with mild and inconspicuous symptoms.

Title: Transmission and clinical characteristics of asymptomatic patients with SARS-CoV-2 infection Content: The 2019 novel coronavirus disease, SARS-CoV-2, is now spreading globally and is characterized by person-to-person transmission. However, it has recently been found that individuals infected with SARS-CoV-2 can be asymptomatic, and simultaneously a source of infection in others. The viral load detected in nasopharyngeal swabs of asymptomatic carriers is relatively high, with a great potential for transmission. More attention should be paid to the insidious spread of disease and harm contributed by asymptomatic SARS-CoV-2 carriers. To provide a theoretical basis for the accurate and early clinical identification of asymptomatic patients, this review objectively summarizes the epidemic status, transmission characteristics and clinical features of asymptomatic patients with SARS-CoV-2 infection.

Title: [Advances on presymptomatic or asymptomatic carrier transmission of COVID-19] Content: COVID-19 is rapidly spreading. Patients in incubation period and healthy carriers are possible sources for transmission. However, such sources of infection cannot be effectively identified due to the symptoms absent. The research evidence is very lacking so far, although there are a few studies suggesting that presymptomatic or asymptomatic carrier may cause COVID-19 transmission. Nearly half of the literature is in the state of preprint without peer review. The question of "the degree to which presymptomatic or asymptomatic infections can transmit" is not fully understood. There is an urgent need to screen infected carriers in larger close contacts or in the general population, and assess their risk for transmission.

Title: [Advances on presymptomatic or asymptomatic carrier transmission of COVID-19]. Content: COVID-19 is rapidly spreading. Patients in incubation period and healthy carriers are possible sources for transmission. However, such sources of infection cannot be effectively identified due to the symptoms absent. The research evidence is very lacking so far, although there are a few studies suggesting that presymptomatic or asymptomatic carrier may cause COVID-19 transmission. Nearly half of the literature is in the state of preprint without peer review. The question of "the degree to which presymptomatic or asymptomatic infections can transmit" is not fully understood. There is an urgent need to screen infected carriers in larger close contacts or in the general population, and assess their risk for transmission.

Title: Comparison of clinical and epidemiological characteristics of asymptomatic and symptomatic SARS-CoV-2 infection: A multi-center study in Sichuan Province, China Content: OBJECTIVES: Asymptomatic infection of SARS-CoV-2 has become a concern worldwide. This study aims to compare the epidemiology and the clinical characteristics of SARS-CoV-2 infection in asymptomatic and symptomatic individuals. METHODS: A total of 511 confirmed SARS-CoV-2 infection cases, including 100 asymptomatic (by the time of the pathogenic tests) and 411 symptomatic individuals were consecutively enrolled from January 25 to February 20, 2020 from hospitals in 21 cities and 47 counties or districts in Sichuan Province. Epidemiological and clinical characteristics were compared. RESULTS: Compared to the symptomatic patients, the asymptomatic cases were younger (P < 0.001), had similar co-morbidity percentages (P = 0.609), and came from higher altitude areas with lower population mobility (P < 0.001) with better defined epidemiological history (P < 0.001). 27.4% of well-documented asymptomatic cases developed delayed symptoms after the pathogenic diagnosis. 60% of asymptomatic cases demonstrated findings of pneumonia on the initial chest CT, including well-recognized features of coronavirus disease-19. None of the asymptomatic individuals died. Two elderly individuals with initially asymptomatic infection developed severe symptoms during hospitalization. One case of possible virus transmission by a patient during the incubation period was highly suspected. CONCLUSIONS: The epidemiological and clinical findings highlight the significance of asymptomatic infection with SARS-CoV-2. Inspecting the epidemiological history would facilitate the identification of asymptomatic cases. Evidence supports the chest CT scans for confirmed asymptomatic cases to evaluate the extent of lung involvement.

Title: Follow up investigation of asymptomatic COVID-19 cases at diagnosis in Busan, Korea. Content: Objectives The objective of the study was to conduct a follow-up investigation of 10 asymptomatic patients at diagnosis among the 98 confirmed COVID-19 cases reported in Busan between February 21 and March 13, 2020 to determine whether asymptomatic infection and transmission during asymptomatic period are possible. Methods The study analyzed 10 asymptomatic, confirmed COVID-19 cases to determine whether asymptomatic infection is possible. We conducted in-depth interviews with patients and guardians; interviews with primary physicians; review of medical records and drug utilization review (DUR) reports; and base station-based location tracking. Results Among the 98, confirmed COVID-19 cases reported in Busan, the study analyzed 10 (10.2%) asymptomatic patients at diagnosis. The Results confirmed that two (2.0%) patients reported to be asymptomatic during the initial epidemiological investigation, but turned symptomatic before diagnosis as per the in-depth interview results. Four cases (4.0%) of early detection led to confirmed diagnosis during the incubation period and presentation of symptoms after diagnosis. In addition, the remaining four patients (4.0%), having no subjective symptoms nor specific findings on chest radiography and Computed Tomography, remained asymptomatic until the isolation order was lifted. With regard to whether transmission during the asymptomatic period is possible, it was found that one out of 23 household contacts of the confirmed patients was identified as an additional confirmed case after coming in close contact with an index patient during the presymptomatic period. Conclusion Among the 98 confirmed cases, asymptomatic infection was confirmed in four cases (4.0%). In addition, there was one additional confirmed case in which the patient was a family member who came in close contact with an index patient during the incubation period, thereby confirming that transmission during the asymptomatic period is possible. The possibility of transmission during the asymptomatic period has been confirmed; therefore, it is necessary to review the measures for expanding contact tracing that is currently being applied starting one day prior to the onset of symptoms.

Title: Follow up investigation of asymptomatic COVID-19 cases at diagnosis in Busan, Korea Content: Objectives: The objective of the study was to conduct a follow-up investigation of 10 asymptomatic patients at diagnosis among the 98 confirmed COVID-19 cases reported in Busan between February 21 and March 13, 2020 to determine whether asymptomatic infection and transmission during asymptomatic period are possible. Methods: The study analyzed 10 asymptomatic, confirmed COVID-19 cases to determine whether asymptomatic infection is possible. We conducted in-depth interviews with patients and guardians; interviews with primary physicians; review of medical records and drug utilization review (DUR) reports; and base station-based location tracking. Results: Among the 98, confirmed COVID-19 cases reported in Busan, the study analyzed 10 (10.2%) asymptomatic patients at diagnosis. The Results confirmed that two (2.0%) patients reported to be asymptomatic during the initial epidemiological investigation, but turned symptomatic before diagnosis as per the in-depth interview results. Four cases (4.0%) of early detection led to confirmed diagnosis during the incubation period and presentation of symptoms after diagnosis. In addition, the remaining four patients (4.0%), having no subjective symptoms nor specific findings on chest radiography and Computed Tomography, remained asymptomatic until the isolation order was lifted. With regard to whether transmission during the asymptomatic period is possible, it was found that one out of 23 household contacts of the confirmed patients was identified as an additional confirmed case after coming in close contact with an index patient during the presymptomatic period. Conclusion: Among the 98 confirmed cases, asymptomatic infection was confirmed in four cases (4.0%). In addition, there was one additional confirmed case in which the patient was a family member who came in close contact with an index patient during the incubation period, thereby confirming that transmission during the asymptomatic period is possible. The possibility of transmission during the asymptomatic period has been confirmed; therefore, it is necessary to review the measures for expanding contact tracing that is currently being applied starting one day prior to the onset of symptoms.

Title: Asymptomatic patients as a source of COVID-19 infections: A systematic review and meta-analysis. Content: BACKGROUND Coronavirus Disease 2019 (COVID-19) is characterised by an unpredictable disease course, ranging from asymptomatic infections to severe, life-threating manifestations. Asymptomatic COVID-19 infections have been described, and the aim of this systematic review was to summarise their presentation form. METHODS We searched PubMed® and Google® (1 December 2019 to 29 March 2020) and extracted age, laboratory findings, and computed tomography (CT) investigations. Pooled incidence rates of clinical characteristics were analysed using random effects models. RESULTS In total, 506 patients from 34 studies (68 single cases and 438 from case series) with an asymptomatic course were identified. Patients with normal radiology were younger (19.59 ± 17.17 years) than patients with abnormal radiology (39.14 ± 26.70 years) (p value = 0.013). Despite being asymptomatic, CT investigations revealed abnormalities in 62.2% of the cases and ground glass opacities were most frequently observed (43.09% by meta-analysis). Most studies reported normal laboratory findings (61.74% by meta-analysis). CONCLUSIONS More than half of patients without any symptoms present with CT abnormalities. Asymptomatic patients may be contagious and thus a potential source of transmission of COVID-19.

Title: Asymptomatic patients as a source of COVID-19 infections: A systematic review and meta-analysis Content: BACKGROUND: Coronavirus Disease 2019 (COVID-19) is characterised by an unpredictable disease course, ranging from asymptomatic infections to severe, life-threating manifestations. Asymptomatic COVID-19 infections have been described, and the aim of this systematic review was to summarise their presentation form. METHODS: We searched PubMed® and Google® (1 December 2019 to 29 March 2020) and extracted age, laboratory findings, and computed tomography (CT) investigations. Pooled incidence rates of clinical characteristics were analysed using random effects models. RESULTS: In total, 506 patients from 34 studies (68 single cases and 438 from case series) with an asymptomatic course were identified. Patients with normal radiology were younger (19.59 ± 17.17 years) than patients with abnormal radiology (39.14 ± 26.70 years) (p value = 0.013). Despite being asymptomatic, CT investigations revealed abnormalities in 62.2% of the cases and ground glass opacities were most frequently observed (43.09% by meta-analysis). Most studies reported normal laboratory findings (61.74% by meta-analysis). CONCLUSIONS: More than half of patients without any symptoms present with CT abnormalities. Asymptomatic patients may be contagious and thus a potential source of transmission of COVID-19.

Title: Comparison of clinical and epidemiological characteristics of asymptomatic and symptomatic SARS-CoV-2 infection: A multi-center study in Sichuan Province, China. Content: OBJECTIVES Asymptomatic infection of SARS-CoV-2 has become a concern worldwide. This study aims to compare the epidemiology and the clinical characteristics of SARS-CoV-2 infection in asymptomatic and symptomatic individuals. METHODS A total of 511 confirmed SARS-CoV-2 infection cases, including 100 asymptomatic (by the time of the pathogenic tests) and 411 symptomatic individuals were consecutively enrolled from January 25 to February 20, 2020 from hospitals in 21 cities and 47 counties or districts in Sichuan Province. Epidemiological and clinical characteristics were compared. RESULTS Compared to the symptomatic patients, the asymptomatic cases were younger (P < 0.001), had similar co-morbidity percentages (P = 0.609), and came from higher altitude areas with lower population mobility (P < 0.001) with better defined epidemiological history (P < 0.001). 27.4% of well-documented asymptomatic cases developed delayed symptoms after the pathogenic diagnosis. 60% of asymptomatic cases demonstrated findings of pneumonia on the initial chest CT, including well-recognized features of coronavirus disease-19. None of the asymptomatic individuals died. Two elderly individuals with initially asymptomatic infection developed severe symptoms during hospitalization. One case of possible virus transmission by a patient during the incubation period was highly suspected. CONCLUSIONS The epidemiological and clinical findings highlight the significance of asymptomatic infection with SARS-CoV-2. Inspecting the epidemiological history would facilitate the identification of asymptomatic cases. Evidence supports the chest CT scans for confirmed asymptomatic cases to evaluate the extent of lung involvement.

Title: How the asymptomatic population is influencing the COVID-19 outbreak in India? Content: According to the current perception, symptomatic, presymptomatic, and asymptomatic infectious persons can infect the healthy population susceptible to the SARS-Cov-2. More importantly, various reports indicate that the number of asymptomatic cases can be several-fold higher than the reported symptomatic cases. In this article, we take the reported cases in India and various states within the country as the specimen to understand the progression of the COVID-19. Employing a modified SEIRD model, we predict the spread of COVID-19 by the symptomatic as well as asymptomatic infectious population. Considering reported infection primarily due to symptomatic we compare the model predicted results with the available data to estimate the dynamics of the asymptomatically infected population. Our data indicate that in the absence of the asymptomatic infectious population, the number of symptomatic cases would have been much less. Therefore, the current progress of the symptomatic infection can be reduced by quarantining the asymptomatically infectious population via extensive or random testing. This study is motivated strictly towards academic pursuit; this theoretical investigation is not meant for influencing policy decisions or public health practices.

Title: Challenges of managing the asymptomatic carriers of SARS-CoV-2 Content: Abstract After an outbreak in Wuhan, China, a growing number of countries are now suffering from an epidemic by SARS-CoV-2, which causes COVID-19. Undoubtedly, reports of the skyrocketing global spread of COVID-19 has shocked people globally, from Japan to the United States.Presently, the World Health Organization indicates that fatality due to COVID-19 is about 2%, inferring that many positive subjects may potentially overcome the illness with mild influenza-like symptoms and no need for hospitalization at intensive-care units. Because COVID-19 is completely new to the human immune system, many throughout the world are likely vulnerable to becoming sick after their initial exposure to SARSCoV-2. Besides hospitalized cases, many individuals are likely asymptomatic but potentially carry the virus. While our knowledge about carriers and their virus shedding is deficient, some studies modelling the viral transmission have considered the potential contribution of the asymptomatic carriers. Protocols for managing asymptomatic cases, for example for controlling them to restrict their contact with healthy people at public places or private residences, have not been established.In-house quarantine may as well be applicable to asymptomatic cases if they could be identified and diagnosed. Presumably now, the asymptomatic subjects potentially contribute to the transmission of COVID-19 without their knowledge, intention or being diagnosed as carriers. Thus, managing the asymptomatic cases, who can carry and likely transmit the virus, is a major healthcare challenge while a pandemic is looming.

Title: Clinical Characteristics of 24 Asymptomatic Infections with COVID-19 Screened among Close Contacts in Nanjing, China Content: Background: Previous studies have showed clinical characteristics of patients with the 2019 novel coronavirus disease (COVID-19) and the evidence of person-to-person transmission. Limited data are available for asymptomatic infections. This study aims to present the clinical characteristics of 24 cases with asymptomatic infection screened from close contacts and to show the transmission potential of asymptomatic COVID-19 virus carriers. Methods: Epidemiological investigations were conducted among all close contacts of COVID-19 patients (or suspected patients) in Nanjing, Jiangsu Province, China, from Jan 28 to Feb 9, 2020, both in clinic and in community. Asymptomatic carriers were laboratory-confirmed positive for the COVID-19 virus by testing the nucleic acid of the pharyngeal swab samples. Their clinical records, laboratory assessments, and chest CT scans were reviewed. Findings: None of the 24 asymptomatic cases presented any obvious symptoms before nucleic acid screening. Five cases (20.8%) developed symptoms (fever, cough, fatigue and etc.) during hospitalization. Twelve (50.0%) cases showed typical CT images of ground-glass chest and five (20.8%) presented stripe shadowing in the lungs. The remaining seven (29.2%) cases showed normal CT image and had no symptoms during hospitalization. These seven cases were younger (median age: 14.0 years; P = 0.012) than the rest. None of the 24 cases developed severe COVID-19 pneumonia or died. The median communicable period, defined as the interval from the first day of positive nucleic acid tests to the first day of continuous negative tests, was 9.5 days (up to 21 days among the 24 asymptomatic cases). Through epidemiological investigation, we observed a typical asymptomatic transmission to the cohabiting family members, which even caused severe COVID-19 pneumonia. Interpretation: The asymptomatic carriers identified from close contacts were prone to be mildly ill during hospitalization. However, the communicable period could be up to three weeks and the communicated patients could develop severe illness. These results highlighted the importance of close contact tracing and longitudinally surveillance via virus nucleic acid tests. Further isolation recommendation and continuous nucleic acid tests may also be recommended to the patients discharged.

Title: The incidence of the novel coronavirus SARS-CoV-2 among asymptomatic patients: a systematic review Content: BACKGROUND: the recent outbreak of the coronavirus disease 2019 (COVID-19) has quickly spread globally since its discovery in Wuhan, China, in December 2019. A comprehensive strategy, including surveillance, diagnostics, research, and clinical treatment is urgently needed to win the battle against COVID-19. Recently, numerous studies reported the incidence of SARS-CoV-2 in asymptomatic patients. Yet, the incidence and viral transmission from the asymptomatic cases are not apparent yet. AIM: this study aims to systematically review the published literature on SARS-CoV-2 in the asymptomatic patients to estimate the incidence of COVID-19 among asymptomatic cases, as well as describe its epidemiological and clinical significance. METHOD: the literature was searched through four scientific databases: PubMed, Web of Science, Scopus, and Science Direct. RESULTS: a total of 63 studies satisfied the inclusion criteria where the majority of the reported studies were from China. However, there was a lack of SARS-CoV-2 epidemiological studies from several countries worldwide, tracing the actual incidence of COVID-19, especially in asymptomatic patients. Studies with a large sample size (n>1000) estimated that percentage of people contracting SARS-CoV-2 and are likely to be asymptomatic ranges from 1.2-12.9%. However, the other studies with a smaller sample size reported a much higher incidence and indicated that up to 87.9% of COVID-19 infected individuals could be asymptomatic. Most of these studies indicated that asymptopatics are a potential source of infection to the community. CONCLUSION: this review highlighted the need for more robust and well-designed studies to better estimate COVID-19 incidence among asymptomatic patients worldwide. The early identification of the asymptomatic cases, as well as monitoring and tracing close contact, could help in mitigating the spread of COVID-19.

Title: The contribution of asymptomatic SARS-CoV-2 infections to transmission - a model-based analysis of the Diamond Princess outbreak Content: Background: Some key gaps in the understanding of SARS-CoV-2 infection remain. One of them is the contribution to transmission from individuals experiencing asymptomatic infections. We aimed to characterise the proportion and infectiousness of asymptomatic infections using data from the outbreak on the Diamond Princess cruise ship. Methods: We used a transmission model of COVID-19 with asymptomatic and presymptomatic states calibrated to outbreak data from the Diamond Princess, to quantify the contribution of asymptomatic infections to transmission. Data available included the date of symptom onset for symptomatic disease for passengers and crew, the number of symptom agnostic tests done each day, and date of positive test for asymptomatic and presymptomatic individuals. Findings: On the Diamond Princess 74% (70-78%) of infections proceeded asymptomatically, i.e. a 1:3.8 case-to-infection ratio. Despite the intense testing 53%, (51-56%) of infections remained undetected, most of them asymptomatic. Asymptomatic individuals were the source for 69% (20-85%) of all infections. While the data did not allow identification of the infectiousness of asymptomatic infections, assuming no or low infectiousness resulted in posterior estimates for the net reproduction number of an individual progressing through presymptomatic and symptomatic stages in excess of 15. Interpretation: Asymptomatic SARS-CoV-2 infections may contribute substantially to transmission. This is essential to consider for countries when assessing the potential effectiveness of ongoing control measures to contain COVID-19.

Title: Testing Asymptomatic Emergency Department Patients for Coronavirus of 2019 (COVID‐19) in a Low Prevalence Region Content: The first cases of Coronavirus of 2019 (COVID‐19) were reported in Wuhan, China in December 2019(1). The literature demonstrates geographical variation with regards to estimates of infection incidence, suggesting that COVID‐19 has been underdiagnosed in certain regions(2,3). The rate of asymptomatic infection has been estimated to be as high as 30.8%, which may help explain variation in incidence, particularly in regions with differing screening practices (3). Transmission of COVID‐19 by asymptomatic carriers has been reported in multiple family units, indicating that this mode of infection is important in understanding disease epidemiology and population risk(4,5).

Title: Identification of RT-PCR-Negative Asymptomatic COVID-19 Patients via Serological Testing Content: Asymptomatic individuals with coronavirus disease (COVID-19) have been identified via nucleic acid testing for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2); however, the epidemiologic characteristics and viral shedding pattern of asymptomatic patients remain largely unknown. In this study, serological testing was applied when identifying nine asymptomatic cases of COVID-19 who showed persistent negative RT-PCR test results for SARS-CoV-2 nucleic acid and no symptoms of COVID-19. Two asymptomatic cases were presumed to be index patients who had cleared the virus when their close contacts developed symptoms of COVID-19. Three of the asymptomatic cases were local individuals who spontaneously recovered before their presumed index patients developed symptoms of COVID-19. This report presents the epidemiologic and clinical characteristics of asymptomatic individuals with SARS-CoV-2 infection that were undetected on RT-PCR tests in previous epidemiologic investigations probably due to the transient viral shedding duration.

Title: The incidence of the novel coronavirus SARS-CoV-2 among asymptomatic patients: a systematic review Content: BACKGROUND: the recent outbreak of the coronavirus disease 2019 (COVID‐19) has quickly spread globally since its discovery in Wuhan, China, in December 2019. A comprehensive strategy, including surveillance, diagnostics, research, and clinical treatment is urgently needed to win the battle against COVID-19. Recently, numerous studies reported the incidence of SARS-CoV-2 in asymptomatic patients. Yet, the incidence and viral transmission from the asymptomatic cases are not apparent yet. AIM: this study aims to systematically review the published literature on SARS-CoV-2 in the asymptomatic patients to estimate the incidence of COVID-19 among asymptomatic cases, as well as describe its epidemiological and clinical significance. METHOD: the literature was searched through four scientific databases: PubMed, Web of Science, Scopus, and Science Direct. RESULTS: a total of 63 studies satisfied the inclusion criteria where the majority of the reported studies were from China. However, there was a lack of SARS-CoV-2 epidemiological studies from several countries worldwide, tracing the actual incidence of COVID-19, especially in asymptomatic patients. Studies with a large sample size (n>1000) estimated that percentage of people contracting SARS-CoV-2 and are likely to be asymptomatic ranges from 1.2-12.9%. However, the other studies with a smaller sample size reported a much higher incidence and indicated that up to 87.9% of COVID-19 infected individuals could be asymptomatic. Most of these studies indicated that asymptopatics are a potential source of infection to the community. CONCLUSION: this review highlighted the need for more robust and well-designed studies to better estimate COVID-19 incidence among asymptomatic patients worldwide. The early identification of the asymptomatic cases, as well as monitoring and tracing close contact, could help in mitigating the spread of COVID-19.

Title: COVID-19 Pneumonia in Asymptomatic Trauma Patients;Report of 8 Cases Content: We are currently involved in the novel coronavirus 2019 (COVID-19) pandemic A considerable number of COVID-19 infected cases are asymptomatic but they can transmit the disease to others, especially healthcare workers In this study, we reported 8 incidentally detected cases of COVID-19 pneumonia in chest computed tomography (CT) scan of patients referred to emergency department following multiple trauma without any respiratory symptoms

Title: Clinical Outcomes in 55 Patients With Severe Acute Respiratory Syndrome Coronavirus 2 Who Were Asymptomatic at Hospital Admission in Shenzhen, China Content: An epidemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has spread unexpectedly in Wuhan, Hubei Province, China, since December 2019. There are few reports about asymptomatic contacts of infected patients identified as positive for SARS-CoV-2 through screening. We studied the epidemiological and clinical outcomes in 55 asymptomatic carriers who were laboratory confirmed to be positive for SARS-CoV-2 through nucleic acid testing of pharyngeal swab samples. The asymptomatic carriers seldom occurred among young people (aged 18–29 years) who had close contact with infected family members. In the majority of patients, the outcome was mild or ordinary 2019 novel coronavirus disease during hospitalization.

Title: Clinical Outcomes in 55 Patients With Severe Acute Respiratory Syndrome Coronavirus 2 Who Were Asymptomatic at Hospital Admission in Shenzhen, China Content: An epidemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has spread unexpectedly in Wuhan, Hubei Province, China, since December 2019. There are few reports about asymptomatic contacts of infected patients identified as positive for SARS-CoV-2 through screening. We studied the epidemiological and clinical outcomes in 55 asymptomatic carriers who were laboratory confirmed to be positive for SARS-CoV-2 through nucleic acid testing of pharyngeal swab samples. The asymptomatic carriers seldom occurred among young people (aged 18-29 years) who had close contact with infected family members. In the majority of patients, the outcome was mild or ordinary 2019 novel coronavirus disease during hospitalization.

Title: Estimating the extent of true asymptomatic COVID-19 and its potential for community transmission: systematic review and meta-analysis Content: Background: The prevalence of true asymptomatic COVID-19 cases is critical to policy makers considering the effectiveness of mitigation measures against the SARS-CoV-2 pandemic. We aimed to synthesize all available research on the asymptomatic rates and transmission rates where possible. Methods: We searched PubMed, Embase, Cochrane COVID-19 trials, and European PMC for pre-print platforms such as MedRxiv. We included primary studies reporting on asymptomatic prevalence where: (a) the sample frame includes at-risk population, and (b) there was sufficiently long follow up to identify pre-symptomatic cases. Meta-analysis used fixed effect and random effects models. Results: We screened 571 articles and included five low risk-of-bias studies from three countries (China (2), USA (2), Italy (1)) that tested 9,242 at-risk people, of which 413 were positive and 65 were asymptomatic. Diagnosis in all studies was confirmed using a RT-qPCR test. The proportion of asymptomatic cases ranged from 6% to 41%. Meta-analysis (fixed effect) found that the proportion of asymptomatic cases was 16% (95% CI: 12% - 20%) overall; higher in non-aged care 19% (15% - 24%), and lower in long-term aged care 8% (4% - 14%). Two studies provided direct evidence of forward transmission of the infection by asymptomatic cases but suggested lower rates than symptomatic cases. Conclusion: Our estimates of the prevalence of asymptomatic COVID-19 cases are lower than many highly publicized studies, but still substantial. Further robust epidemiological evidence is urgently needed, including in sub-populations such as children, to better understand the importance of asymptomatic cases for driving spread of the pandemic.

Title: Viral dynamics in asymptomatic patients with COVID-19 Content: Abstract Data are limited on the viral load, viral shedding patterns and potential infectivity of asymptomatic patients (APs) with coronavirus disease 2019 (COVID-19). We included 31 adult patients who were virologically confirmed to have COVID-19 but were asymptomatic on admission. Among these 31 patients, 22 presented symptoms after admission and were defined as asymptomatic patients in incubation period (APIs); the other 9 patients remained asymptomatic during hospitalization and were defined as asymptomatic patients (APs). The cycle threshold (Ct) values of APs (39.0, IQR 37.5-39.5) was significantly higher than those of APIs (34.5, IQR 32.2-37.0), which indicated a lower viral load in APs, but the duration of viral shedding remained similar between the two groups (7 days IQR 5-14 vs. 8 days IQR 5-16). The study findings demonstrated that although they have a lower viral load, APs with COVID-19 still have certain period of viral shedding, which suggests the possibility of transmission during their asymptomatic period. Further longitudinal surveillance of these asymptomatic cases via virus nucleic acid tests are warranted.

Title: [Asymptomatic and pre-symptomatic cases of COVID-19 contribution to spreading the epidemic and need for targeted control strategies]. Content: The asymptomatic carrier state of COVID-19 has become a topic of concern for preventing a possible epidemic rebound. This review describes and defines the COVID-19 asymptomatic carrier state and outlines methods for identifying counting and reporting these cases. The author elaborates that the asymptomatic carrier state can be further divided into asymptomatic infection and pre-symptomatic infection after extended follow-up based on the nature of disease progression. The author presents the limited available data about infectiousness of asymptomatic and pre-symptomatic cases and their possible contributions to the overall epidemic of COVID-19 observed so far in China. Challenges of a possible second epidemic wave of COVID-19 caused by asymptomatic and pre-symptomatic cases are discussed and suggestions for control strategies and scientific research are provided.

Title: Risk factors for disease progression in COVID-19 patients Content: BACKGROUND: Coronavirus disease (COVID-19) is rapidly spreading worldwide. Although 10-20% of patients with COVID-19 have severe symptoms, little is known about the risk factors related to the aggravation of COVID-19 symptoms from asymptomatic or mild to severe disease states. METHODS: This retrospective study included 211 patients who were asymptomatic or with mild presentations of COVID-19. We evaluated the differences in demographic and clinical data between the cured (discharged to home) and transferred (aggravated to severe-stage COVID-19) groups. RESULTS: A multivariate logistic analysis showed that body temperature, chills, initial chest X-ray findings, and the presence of diabetes were significantly associated with predicting the progression to severe stage of COVID-19 (p < 0.05). The odds ratio of transfer in patients with COVID-19 increased by 12.7-fold for abnormal findings such as haziness or consolidation in initial chest X-ray, 6.32-fold for initial symptom of chills, and 64.1-fold for diabetes. CONCLUSIONS: Even if patients are asymptomatic or have mild symptoms, clinicians should closely observe patients with COVID-19 presenting with chills, body temperature > 37.5 °C, findings of pneumonia in chest X-ray, or diabetes.

Title: Risk factors for disease progression in COVID-19 patients Content: BACKGROUND: Coronavirus disease (COVID-19) is rapidly spreading worldwide. Although 10–20% of patients with COVID-19 have severe symptoms, little is known about the risk factors related to the aggravation of COVID-19 symptoms from asymptomatic or mild to severe disease states. METHODS: This retrospective study included 211 patients who were asymptomatic or with mild presentations of COVID-19. We evaluated the differences in demographic and clinical data between the cured (discharged to home) and transferred (aggravated to severe-stage COVID-19) groups. RESULTS: A multivariate logistic analysis showed that body temperature, chills, initial chest X-ray findings, and the presence of diabetes were significantly associated with predicting the progression to severe stage of COVID-19 (p < 0.05). The odds ratio of transfer in patients with COVID-19 increased by 12.7-fold for abnormal findings such as haziness or consolidation in initial chest X-ray, 6.32-fold for initial symptom of chills, and 64.1-fold for diabetes. CONCLUSIONS: Even if patients are asymptomatic or have mild symptoms, clinicians should closely observe patients with COVID-19 presenting with chills, body temperature > 37.5 °C, findings of pneumonia in chest X-ray, or diabetes.

Title: Chest Computed Tomography Findings in Asymptomatic Patients with COVID-19 Content: Background: Little is known about the damage to the respiratory system in asymptomatic patients with coronavirus disease (COVID-19). Objective: Herein, we evaluated the findings of chest computed tomography (CT) and radiography in patients with COVID-19 who were asymptomatic. Methods: We retrospectively investigated patients with a confirmed diagnosis of COVID-19 but who did not show any symptoms. Among the 139 patients with COVID-19 who were hospitalized, 10 (7.2%) were asymptomatic. Their chest CT and radiographic findings were analyzed. Results: In the results, all patients (100%) had ground glass opacity (GGO) on chest CT. Further, the GGO lesions were predominantly distributed peripherally and posteriorly in all patients. In 9 (90%) patients, the GGO lesions were combined with reticular opacity. Air-bronchogram due to bronchiolectasis surrounded by GGO was observed in 8 patients (80%). Additionally, the lung lesions were dominant on the right side in all patients. Conclusions: In conclusion, considering our results that the lung is affected in asymptomatic patients, it will be necessary to extend the indications of COVID-19 testing for effective management of COVID-19 during the pandemic.

Title: Transmission potential of asymptomatic and paucisymptomatic SARS-CoV-2 infections: a three-family cluster study in China Content: Data concerning the transmission of SARS-CoV-2 in asymptomatic and paucisymptomatic patients are lacking. We report a three-family cluster of infections involving asymptomatic and paucisymptomatic transmission. Eight (53%) of 15 members from three families were confirmed with SARS-CoV-2 infection. Of eight patients, three were asymptomatic and one was paucisymptomatic. An asymptomatic mother transmitted the virus to her son, and a paucisymptomatic father transmitted the virus to his three-month-old daughter. SARS-CoV-2 was detected in the environment of one household. The complete genomes of SARS-CoV-2 from the patients were >99.9% identical and were clustered with other SARS-CoV-2 sequences reported from China and other countries.

Title: A retrospective analysis of the epidemiology, clinical manifestations, and imaging characteristics of familial cluster-onset COVID-19. Content: Background The coronavirus disease 2019 (COVID-19) virus has a high incidence rate and strong infectivity. The diagnosis and evaluation of familial outbreaks requires a collective consideration of epidemiological history, molecular detection methods, chest computed tomography (CT), and clinical symptoms. Methods A group of family patients with COVID-19 diagnosed in Guizhou, China, in February 2020, was retrospectively analyzed. As of March 1, all patients in the group have been discharged from hospital. This study tracked all patients in the group. We report the epidemiology, radiological characteristics, treatment, and clinical outcomes of these patients. Results We collected a group of 8 clustered cases (3 men and 5 women) from a family with confirmed COVID-19 infection. In the first admission diagnosis, according to the degree of clinical symptoms, the 8 patients were defined as mild type (4/8) or moderate type (4/8). They were also divided according to the CT findings into early period (1/8), progressive period (3/8), and negative on CT scan (4/8); for the first 4 patients, the corresponding CT image scores were 1, 4, 5, and 5 respectively. In this group of COVID-19 patients, half of the patients showed occult clinical manifestations and negative CT performance. We defined these patients as COVID-19-infected patients, or asymptomatic carriers. Conclusions The family cluster analysis indicated that COVID-19-infected patients (asymptomatic carriers) and symptomatic COVID-19 patients are distinct but coexistent. This may indicate that the infectivity and virulence of severe acute respiratory syndrome coronavirus 2 (SARS-COV-2) has decreased. In order to block the transmission pathway of this virus before it spreads, we need to identify the presence of asymptomatic carriers as early as possible.

Title: The prevalence of antibodies to SARS-CoV-2 in asymptomatic healthcare workers with intensive exposure to COVID-19 Content: The prevalence of asymptomatic SARS-CoV-2 infection in healthcare workers with intensive exposure to COVID-19 is unclear. In this study, we investigated the seroprevalence of SARS-CoV-2 in 797 asymptomatic healthcare workers with intensive exposure to COVID-19 patients in Wuhan, China. Positive IgG was detected from 35 asymptomatic healthcare workers, and the prevalence of antibodies to SARS-CoV-2 in asymptomatic healthcare workers was 4.39% (35/797). None of them developed COVID-19 until May 15. 33 of them have performed at least one chest CT scan showing no viral pneumonia features, and 16 have finished at least one-time SARS-CoV-2 RNA detection with negative results. When contacting with the patients, 15 of them dressed with full personal protective equipment (PPE), and 16 worn N95 mask and gown. To the best of our knowledge, this is the first investigation reported that the seroprevalence of SARS-CoV-2 was 4.39% in asymptomatic healthcare workers with applied PPE in a high epidemic area, which may provide useful information of estimating asymptomatic infection rate in general population.

Title: The natural history and transmission potential of asymptomatic SARS-CoV-2 infection Content: BACKGROUND: Little is known about the natural history of asymptomatic SARS-CoV-2 infection or its contribution to infection transmission. METHODS: We conducted a prospective study at a quarantine center for COVID-19 in Ho Chi Minh City, Vietnam. We enrolled quarantined people with RT-PCR-confirmed SARS-CoV-2 infection, collecting clinical data, travel and contact history, and saliva at enrolment and daily nasopharyngeal throat swabs (NTS) for RT-PCR testing. We compared the natural history and transmission potential of asymptomatic and symptomatic individuals. RESULTS: Between March 10(th) and April 4(th), 2020, 14,000 quarantined people were tested for SARS-CoV-2; 49 were positive. Of these, 30 participated in the study: 13(43%) never had symptoms and 17(57%) were symptomatic. 17(57%) participants acquired their infection outside Vietnam. Compared with symptomatic individuals, asymptomatic people were less likely to have detectable SARS-CoV-2 in NTS samples collected at enrolment (8/13 (62%) vs. 17/17 (100%) P=0.02). SARS-CoV-2 RNA was detected in 20/27 (74%) available saliva; 7/11 (64%) in the asymptomatic and 13/16 (81%) in the symptomatic group (P=0.56). Analysis of the probability of RT-PCR positivity showed asymptomatic participants had faster viral clearance than symptomatic participants (P<0.001 for difference over first 19 days). This difference was most pronounced during the first week of follow-up. Two of the asymptomatic individuals appeared to transmit the infection to up to four contacts. CONCLUSIONS: Asymptomatic SARS-CoV-2 infection is common and can be detected by analysis of saliva or NTS. NTS viral loads fall faster in asymptomatic individuals, but they appear able to transmit the virus to others.

Title: Clinical characteristics of COVID-19 in 104 people with SARS-CoV-2 infection on the Diamond Princess cruise ship: a retrospective analysis Content: BACKGROUND: The ongoing COVID-19 pandemic is a global threat. Identification of markers for symptom onset and disease progression is a pressing issue. We described the clinical features of people infected on board the Diamond Princess cruise ship who were diagnosed with asymptomatic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection or mild or severe COVID-19, on admission to the Self-Defense Forces Central Hospital (Tokyo, Japan) and at the end of observation. METHODS: This retrospective, single-centre study included participants with laboratory-detected SARS-CoV-2 infection who were admitted to the Self-Defense Forces Central Hospital from Feb 11 to Feb 25, 2020. Clinical records, laboratory data, and radiological findings were analysed. Clinical outcomes were followed up until discharge or Feb 26, 2020, whichever came first. We defined asymptomatic infection as SARS-CoV-2 infection with no history of clinical signs and symptoms, severe COVID-19 as clinical symptoms of pneumonia (dyspnoea, tachypnoea, peripheral capillary oxygen saturation <93%, and need for oxygen therapy), and mild COVID-19 as all other symptoms. Clinical features on admission were compared among patients with different disease severity, including asymptomatic infection, at the end of observation. We used univariable analysis to identify factors associated with symptomatic illness among asymptomatic people infected with SARS-CoV-2 and disease progression in patients with COVID-19. FINDINGS: Among the 104 participants included in the final analysis, the median age was 68 years (IQR 47-75) and 54 (52%) were male. On admission, 43 (41%) participants were classified as asymptomatic, 41 (39%) as having mild COVID-10, and 20 (19%) as having severe COVID-19. At the end of observation, 33 (32%) participants were confirmed as being asymptomatic, 43 (41%) as having mild COVID-19, and 28 (27%) as having severe COVID-19. Serum lactate hydrogenase concentrations were significantly higher in the ten participants who were asymptomatic on admission but developed symptomatic COVID-19 compared with the 33 participants who remained asymptomatic throughout the observation period (five [50%] vs four [12%] participants; odds ratio 7·25, 95% CI 1·43-36·70; p=0·020). Compared with patients with mild disease at the end of observation, patients with severe COVID-19 were older (median age 73 years [IQR 55-77] vs 60 years [40-71]; p=0·028) and had more frequent consolidation on chest CT (13 [46%] of 28 vs nine [21%] of 43; p=0·035) and lymphopenia (16 [57%] vs ten [23%]; p=0·0055) on admission. INTERPRETATION: Older age, consolidation on chest CT images, and lymphopenia might be risk factors for disease progression of COVID-19 and contribute to improved clinical management. FUNDING: None.

Title: Clinical characteristics of COVID-19 in 104 people with SARS-CoV-2 infection on the Diamond Princess cruise ship: a retrospective analysis Content: BACKGROUND: The ongoing COVID-19 pandemic is a global threat. Identification of markers for symptom onset and disease progression is a pressing issue. We described the clinical features of people infected on board the Diamond Princess cruise ship who were diagnosed with asymptomatic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection or mild or severe COVID-19, on admission to the Self-Defense Forces Central Hospital (Tokyo, Japan) and at the end of observation. METHODS: This retrospective, single-centre study included participants with laboratory-detected SARS-CoV-2 infection who were admitted to the Self-Defense Forces Central Hospital from Feb 11 to Feb 25, 2020. Clinical records, laboratory data, and radiological findings were analysed. Clinical outcomes were followed up until discharge or Feb 26, 2020, whichever came first. We defined asymptomatic infection as SARS-CoV-2 infection with no history of clinical signs and symptoms, severe COVID-19 as clinical symptoms of pneumonia (dyspnoea, tachypnoea, peripheral capillary oxygen saturation <93%, and need for oxygen therapy), and mild COVID-19 as all other symptoms. Clinical features on admission were compared among patients with different disease severity, including asymptomatic infection, at the end of observation. We used univariable analysis to identify factors associated with symptomatic illness among asymptomatic people infected with SARS-CoV-2 and disease progression in patients with COVID-19. FINDINGS: Among the 104 participants included in the final analysis, the median age was 68 years (IQR 47–75) and 54 (52%) were male. On admission, 43 (41%) participants were classified as asymptomatic, 41 (39%) as having mild COVID-10, and 20 (19%) as having severe COVID-19. At the end of observation, 33 (32%) participants were confirmed as being asymptomatic, 43 (41%) as having mild COVID-19, and 28 (27%) as having severe COVID-19. Serum lactate hydrogenase concentrations were significantly higher in the ten participants who were asymptomatic on admission but developed symptomatic COVID-19 compared with the 33 participants who remained asymptomatic throughout the observation period (five [50%] vs four [12%] participants; odds ratio 7·25, 95% CI 1·43–36·70; p=0·020). Compared with patients with mild disease at the end of observation, patients with severe COVID-19 were older (median age 73 years [IQR 55–77] vs 60 years [40–71]; p=0·028) and had more frequent consolidation on chest CT (13 [46%] of 28 vs nine [21%] of 43; p=0·035) and lymphopenia (16 [57%] vs ten [23%]; p=0·0055) on admission. INTERPRETATION: Older age, consolidation on chest CT images, and lymphopenia might be risk factors for disease progression of COVID-19 and contribute to improved clinical management. FUNDING: None.

Title: Asymptomatic COVID-19 Have Longer Treatment Cycle Than Moderate Type of Confirmed Patients Content: IMPORTANCE A kind of pneumonia caused by unknown causes that occurred in Wuhan, Hubei, China in December 2019, was reported as a result of novel coronavirus infection on January 7, 2020, and then WHO named it "COVID-19". The comparison of epidemiological and clinical characteristics for those patients between asymptomatic COVID-19 infections and moderate type of confirmed cases is limited. OBJECTIVE To compare the difference of epidemiology and clinical characteristics between asymptomatic COVID-19 infections and moderate type of confirmed cases. DESIGN, SETTING, AND PARTICIPANTS Retrospective, single-center cohort study of COVID-19 involving 52 infections of both 26 asymptomatic and 26 moderate type of confirmed cases in the recovery stage at Guizhou Provincial Staff Hospital in Guiyang, China, from January 29, to March 31, 2020; final date of follow-up was April 22. This study was registered in Chinese Clinical Trial Registry Center. EXPOSURES Documented the asymptomatic COVID-19 infections and moderate type of confirmed cases. MAIN OUTCOMES AND MEASURES Epidemiological, demographic, clinical, laboratory, radiological, and treatment data were collected and analyzed. Epidemiological and clinical characteristics of asymptomatic COVID-19 infections and moderate type of confirmed cases were compared. RESULTS The median treatment cycle of asymptomatic COVID-19 infections was 16 days (interquartile range, 11-20 days) and longer than 13 days (interquartile range, 10-15 days) of moderate type of confirmed cases (p=0.049). The median incubation period of asymptomatic COVID-19 infections was 10 days (interquartile range, 0-21 days), while the control group was 7 days (interquartile range, 1-15 days) (p=0.27). On the initial chest computerized tomography (CT) check, 18 (69.2%, 18/26) asymptomatic COVID-19 infections were no imaging changes, which was of no significance compared with 12 (46.2%, 12/26) patients with moderate type of confirmed patients (p=0.092). CONCLUSIONS AND RELEVANCE In this single-center study, we found that asymptomatic COVID-19 infections have longer treatment cycle than those moderate type of confirmed cases.

Title: Transmission Potential of Asymptomatic and Paucisymptomatic Severe Acute Respiratory Syndrome Coronavirus 2 Infections: A 3-Family Cluster Study in China Content: Data concerning the transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in asymptomatic and paucisymptomatic patients are lacking. We report a 3-family cluster of infections involving asymptomatic and paucisymptomatic transmission. Eight of 15 (53%) members from 3 families were confirmed with SARS-CoV-2 infection. Of 8 patients, 3 were asymptomatic and 1 was paucisymptomatic. An asymptomatic mother transmitted the virus to her son, and a paucisymptomatic father transmitted the virus to his 3-month-old daughter. SARS-CoV-2 was detected in the environment of 1 household. The complete genomes of SARS-CoV-2 from the patients were > 99.9% identical and were clustered with other SARS-CoV-2 sequences reported from China and other countries.

Title: COVID-19 Pneumonia in Asymptomatic Trauma Patients; Report of 8 Cases. Content: We are currently involved in the novel coronavirus 2019 (COVID-19) pandemic. A considerable number of COVID-19 infected cases are asymptomatic but they can transmit the disease to others, especially healthcare workers. In this study, we reported 8 incidentally detected cases of COVID-19 pneumonia in chest computed tomography (CT) scan of patients referred to emergency department following multiple trauma without any respiratory symptoms.

Title: COVID-19 Pneumonia in Asymptomatic Trauma Patients; Report of 8 Cases Content: We are currently involved in the novel coronavirus 2019 (COVID-19) pandemic. A considerable number of COVID-19 infected cases are asymptomatic but they can transmit the disease to others, especially healthcare workers. In this study, we reported 8 incidentally detected cases of COVID-19 pneumonia in chest computed tomography (CT) scan of patients referred to emergency department following multiple trauma without any respiratory symptoms.

Title: Clinical outcome of 55 asymptomatic cases at the time of hospital admission infected with SARS-Coronavirus-2 in Shenzhen, China ;The Journal of Infectious Diseases ;Oxford Academic Content: Abstract An epidemic caused by SARS-Coronavirus-2 infection has spread unexpectedly in Wuhan, Hubei Province, China since December 2019 It is rarely reported about asymptomatic cases screened from close contacts We study epidemiological and clinical outcome of 55 asymptomatic carriers who were laboratory-confirmed positive for the SARS-Coronavirus-2 by testing the nucleic acid of the pharyngeal swab samples The evidence showed that asymptomatic carriers occurred more often in middle aged people who had close contact with infected family members The majority of the cases developed to be mild and ordinary COVID-19 during hospital

Title: Epidemiological and clinical features of asymptomatic patients with SARS-CoV-2 infection Content: Few studies reported the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infected patients with completely asymptomatic throughout the disease course. We investigated the epidemiological and clinical features of patients infected by SARS-CoV-2 without any symptoms. Patients with confirmed SARS-CoV-2 infection were retrospectively recruited. The demographic characteristics, clinical data, treatment, and outcomes of SARS-CoV-2 infected patients without any symptoms were analyzed. Fifteen (4.4%) of 342 SARS-CoV-2 infected patients did not develop any symptom during the course of the disease. The median time from exposure to diagnosis was 7.0 days (interquartile range [IQR]: 1.0-15.0 days). Of the 15 patients, 14 patients were diagnosed by tested positive for SARS-CoV-2 in throat swabs, while one patient was only tested positive for SARS-CoV-2 in anal swabs. During hospitalization, only 1 (6.7%) patient developed lymphopenia. Abnormalities of chest computed tomography examinations were detected in 8 (53.4%) patients on admission. As of 8 March 2020, all patients have been discharged. The median time of SARS-CoV-2 tested negative from admission was 7.0 days (IQR: 4.0-9.0 days). Patients without any symptoms but with SARS-CoV-2 exposure should be closely monitored and tested for SARS-CoV-2 both in anal and throat swabs to excluded the infection. Asymptomatic patients infected by SARS-CoV-2 have favorable outcomes.

Title: High incidence of asymptomatic SARS-CoV-2 infection, Chongqing, China Content: Background: SARS-CoV-2 has been a global pandemic, but the emergence of asymptomatic patients has caused difficulties in the prevention of the epidemic. Therefore, it is significant to understand the epidemiological characteristics of asymptomatic patients with SARS-CoV-2 infection. Methods: In this single-center, retrospective and observational study, we collected data from 167 patients with SARS-CoV-2 infection treated in Chongqing Public Health Medical Center (Chongqing, China) from January to March 2020. The epidemiological characteristics and variable of these patients were collected and analyzed. Findings: 82.04% of the SARS-CoV-2 infected patients had a travel history in Wuhan or a history of contact with returnees from Wuhan, showing typical characteristics of imported cases, and the proportion of severe Covid-19 patients was 13.2%, of which 59% were imported from Wuhan. For the patients who was returnees from Wuhan, 18.1% was asymptomatic patients. In different infection periods, compared with the proportion after 1/31/2020, the proportion of asymptomatic patient among SARS-CoV-2 infected patient was higher(19% VS 1.5%). In different age groups, the proportion of asymptomatic patient was the highest(28.6%) in children group under 14, next in elder group over 70 (27.3%). Compared with mild and common Covid-19 patients, the mean latency of asymptomatic was longer (11.25 days VS 8.86 days), but the hospital length of stay was shorter (14.3 days VS 16.96 days) . Conclusion: The SARS-CoV-2 prevention needs to focus on the screening of asymptomatic patients in the community with a history of contact with the imported population, especially for children and the elderly population.

Title: Asymptomatic patients and asymptomatic phases of Coronavirus Disease 2019 (COVID-19): a population-based surveillance study Content: In this population-based study, we identified 307 confirmed COVID-19 cases from massive surveillance, including 129,551 individuals screened at fever clinics or returning from Hubei and 3710 close contacts of confirmed COVID-19 patients. Among them, 17 patients were asymptomatic at initial clinical assessment. These asymptomatic patients on admission accounted for a small proportion of all patients (5.54%) with relatively weak transmissibility, and the detection rate was 0.35 per 100 close contacts. Moreover, the dynamics of symptoms of the 307 patients showed that the interval from symptom remission to the final negativity of viral nucleic acid was 5.0 days (IQR 2.0 to 11.0 days), with 14 patients (4.56%) having re-detectable viral RNA after discharge. Together, our findings suggested asymptomatic carriers and presymptomatic patients only accounted for a small proportion of COVID-19. Also, the asymptomatic phase in during recovery of COVID-19 urged that negativity in viral RNA is necessary as de-isolation criteria and follow-up is recommended.

Title: A considerable proportion of individuals with asymptomatic SARS-CoV-2 infection in Tibetan population Content: Severe acute respiratory syndrome coronavirus 2 (SARS-Cov-2) quickly became a major epidemic threat in the whole China. We analysed SARS-Cov-2 infected cases from Tibetan Autonomous Prefecture, and noted divergent characteristics of these Tibetans infected cases compared to Han Chinese, characterizing by a considerable proportion of asymptomatic carriers (21.7%), and few symptomatic patients with initial symptom of fever (7.7%). Here, we did a descriptive study on clinical characteristics of 18 asymptomatic individuals with SARS-CoV-2 infection. The median age of these asymptomatic carriers was 31 years and one third of them were students, aged under 20 years. Notably, some of asymptomatic carriers had recognizable changes in radiological and laboratory indexes. Our finding indicates a potentially big number of SARS-CoV-2 asymptomatic carriers in prevalent area, highlighting a necessity of screening individuals with close contact of infected patients, for a better control on the spread of SARS-CoV-2 infection.

Title: The natural history and transmission potential of asymptomatic SARS-CoV-2 infection Content: Background: Little is known about the natural history of asymptomatic SARS-CoV-2 infection or its contribution to infection transmission. Methods: We conducted a prospective study at a quarantine centre for COVID-19 in Ho Chi Minh City, Vietnam. We enrolled quarantined people with RT-PCR-confirmed SARS-CoV-2 infection, collecting clinical data, travel and contact history, and saliva at enrolment and daily nasopharyngeal throat swabs (NTS) for RT-PCR testing. We compared the natural history and transmission potential of asymptomatic and symptomatic individuals. Results: Between March 10th and April 4th, 2020, 14,000 quarantined people were tested for SARS-CoV-2; 49 were positive. Of these, 30 participated in the study: 13(43%) never had symptoms and 17(57%) were symptomatic. 17(57%) participants acquired their infection outside Vietnam. Compared with symptomatic individuals, asymptomatic people were less likely to have detectable SARS-CoV-2 in NTS samples collected at enrolment (8/13 (62%) vs. 17/17 (100%) P=0.02). SARS-CoV-2 RNA was detected in 20/27 (74%) available saliva; 7/11 (64%) in the asymptomatic and 13/16 (81%) in the symptomatic group (P=0.56). Analysis of the probability of RT-PCR positivity showed asymptomatic participants had faster viral clearance than symptomatic participants (P<0.001 for difference over first 19 days). This difference was most pronounced during the first week of follow-up. Two of the asymptomatic individuals appeared to transmit the infection to up to four contacts. Conclusions: Asymptomatic SARS-CoV-2 infection is common and can be detected by analysis of saliva or NTS. NTS viral loads fall faster in asymptomatic individuals, but they appear able to transmit the virus to others.

Title: The natural history and transmission potential of asymptomatic SARS-CoV-2 infection Content: BACKGROUND: Little is known about the natural history of asymptomatic SARS-CoV-2 infection or its contribution to infection transmission. METHODS: We conducted a prospective study at a quarantine center for COVID-19 in Ho Chi Minh City, Vietnam. We enrolled quarantined people with RT-PCR-confirmed SARS-CoV-2 infection, collecting clinical data, travel and contact history, and saliva at enrolment and daily nasopharyngeal throat swabs (NTS) for RT-PCR testing. We compared the natural history and transmission potential of asymptomatic and symptomatic individuals. RESULTS: Between March 10th and April 4th, 2020, 14,000 quarantined people were tested for SARS-CoV-2; 49 were positive. Of these, 30 participated in the study: 13(43%) never had symptoms and 17(57%) were symptomatic. 17(57%) participants acquired their infection outside Vietnam. Compared with symptomatic individuals, asymptomatic people were less likely to have detectable SARS-CoV-2 in NTS samples collected at enrolment (8/13 (62%) vs. 17/17 (100%) P=0.02). SARS-CoV-2 RNA was detected in 20/27 (74%) available saliva; 7/11 (64%) in the asymptomatic and 13/16 (81%) in the symptomatic group (P=0.56). Analysis of the probability of RT-PCR positivity showed asymptomatic participants had faster viral clearance than symptomatic participants (P<0.001 for difference over first 19 days). This difference was most pronounced during the first week of follow-up. Two of the asymptomatic individuals appeared to transmit the infection to up to four contacts. CONCLUSIONS: Asymptomatic SARS-CoV-2 infection is common and can be detected by analysis of saliva or NTS. NTS viral loads fall faster in asymptomatic individuals, but they appear able to transmit the virus to others.

Title: COVID‐19 suspicion and diagnosis: are we still chasing epidemiological criteria? Content: Italy was the second nation after China to be most involved into the COVID‐19 outbreak. From the beginning, much attention has been attributed to the importance of epidemiological criteria (such as previous contact with confirmed COVID‐19 cases, recent journey across China or the northern Italian regions) in order to assess a suspected patient for SARS‐CoV‐2 infection. Despite this, by now evidences do exist about the possibly huge reservoir of asymptomatic patients and its underestimated ability to spread the infection. Thus, we do believe that when an infectious disease has a big ratio of asymptomatic cases, as for COVID‐19, it is simply not safe to rely on epidemiological criteria and we briefly discuss this issue throughout the few new evidences there are about. This article is protected by copyright. All rights reserved.

Title: Prevention of COVID-19 infection in the medical population: a possible help from anosmia? Content: COVID-19 asymptomatic cases increases the risks of disease dissemination with even greater risk for physicians given the shortage of personal protective equipment. Here we report on the consistent finding of frequent presentation of anosmia or hyposmia in COVID-19 patients, even in the absence of other symptoms and without other olfactory or nasal findings. In the uncertainty of the clinical characteristics of these patients, this symptom can be a tool to reduce the spread of the infection between medical population.

Title: Prevention of COVID-19 infection in the medical population: a possible help from anosmia?. Content: COVID-19 asymptomatic cases increases the risks of disease dissemination with even greater risk for physicians given the shortage of personal protective equipment. Here we report on the consistent finding of frequent presentation of anosmia or hyposmia in COVID-19 patients, even in the absence of other symptoms and without other olfactory or nasal findings. In the uncertainty of the clinical characteristics of these patients, this symptom can be a tool to reduce the spread of the infection between medical population.

Title: COVID-19: asymptomatic carrier transmission is an underestimated problem Content: At the present time, COVID-19 is spreading rapidly [1]. The global prevention and control of COVID-19 is focused on the estimation of the relevant incubation period, basic reproduction number (R0), effective reproduction number (Rt) and death risk. Although the prevention and control of COVID-19 requires a reliable estimation of the relevant incubation period, R0, Rt and death risk. Another key epidemiological parameter-asymptomatic ratio that provides strength and range for social alienation strategies of COVID-19, which is widely defined as the proportion of asymptomatic infections among all disease infections. In fact, the ratio of asymptomatic infection is a useful indicator of the burden of disease and a better measurement of the transmissibility of the virus. So far, people have not paid enough attention to asymptomatic carriers. The asymptomatic carriers discussed in this study are recessive infections, that is, those who have never shown symptoms after onset of infection. We will discuss three aspects: detection, infectivity and proportion of healthy carriers.

Title: Intraoperative Diagnosis of Coronavirus Disease 2019 in an Asymptomatic Patient: A Case Report Content: Patients with coronavirus disease 2019 (COVID-19) with variable clinical presentations are encountered in the perioperative setting. While some have already been diagnosed and are symptomatic, others have undiagnosed, asymptomatic COVID-19. The latter group poses the greatest risk of transmission. Given limited capacities in most health care systems, diagnostic testing is mainly performed in symptomatic patients or those with relevant exposure. We report an intraoperative diagnosis of COVID-19 in an asymptomatic patient, prompted by clinical signs. To control a pandemic such as COVID-19, a high index of suspicion is pivotal when caring for asymptomatic patients in the perioperative setting.

Title: Signs and symptoms to determine if a patient presenting in primary care or hospital outpatient settings has COVID-19 disease. Content: BACKGROUND Some people with SARS-CoV-2 infection remain asymptomatic, whilst in others the infection can cause mild to moderate COVID-19 disease and COVID-19 pneumonia, leading some patients to require intensive care support and, in some cases, to death, especially in older adults. Symptoms such as fever or cough, and signs such as oxygen saturation or lung auscultation findings, are the first and most readily available diagnostic information. Such information could be used to either rule out COVID-19 disease, or select patients for further diagnostic testing. OBJECTIVES To assess the diagnostic accuracy of signs and symptoms to determine if a person presenting in primary care or to hospital outpatient settings, such as the emergency department or dedicated COVID-19 clinics, has COVID-19 disease or COVID-19 pneumonia. SEARCH METHODS On 27 April 2020, we undertook electronic searches in the Cochrane COVID-19 Study Register and the University of Bern living search database, which is updated daily with published articles from PubMed and Embase and with preprints from medRxiv and bioRxiv. In addition, we checked repositories of COVID-19 publications. We did not apply any language restrictions. SELECTION CRITERIA Studies were eligible if they included patients with suspected COVID-19 disease, or if they recruited known cases with COVID-19 disease and controls without COVID-19. Studies were eligible when they recruited patients presenting to primary care or hospital outpatient settings. Studies including patients who contracted SARS-CoV-2 infection while admitted to hospital were not eligible. The minimum eligible sample size of studies was 10 participants. All signs and symptoms were eligible for this review, including individual signs and symptoms or combinations. We accepted a range of reference standards including reverse transcription polymerase chain reaction (RT-PCR), clinical expertise, imaging, serology tests and World Health Organization (WHO) or other definitions of COVID-19. DATA COLLECTION AND ANALYSIS Pairs of review authors independently selected all studies, at both title and abstract stage and full-text stage. They resolved any disagreements by discussion with a third review author. Two review authors independently extracted data and resolved disagreements by discussion with a third review author. Two review authors independently assessed risk of bias using the QUADAS-2 checklist. Analyses were descriptive, presenting sensitivity and specificity in paired forest plots, in ROC (receiver operating characteristic) space and in dumbbell plots. We did not attempt meta-analysis due to the small number of studies, heterogeneity across studies and the high risk of bias. MAIN RESULTS We identified 16 studies including 7706 participants in total. Prevalence of COVID-19 disease varied from 5% to 38% with a median of 17%. There were no studies from primary care settings, although we did find seven studies in outpatient clinics (2172 participants), and four studies in the emergency department (1401 participants). We found data on 27 signs and symptoms, which fall into four different categories: systemic, respiratory, gastrointestinal and cardiovascular. No studies assessed combinations of different signs and symptoms and results were highly variable across studies. Most had very low sensitivity and high specificity; only six symptoms had a sensitivity of at least 50% in at least one study: cough, sore throat, fever, myalgia or arthralgia, fatigue, and headache. Of these, fever, myalgia or arthralgia, fatigue, and headache could be considered red flags (defined as having a positive likelihood ratio of at least 5) for COVID-19 as their specificity was above 90%, meaning that they substantially increase the likelihood of COVID-19 disease when present. Seven studies carried a high risk of bias for selection of participants because inclusion in the studies depended on the applicable testing and referral protocols, which included many of the signs and symptoms under study in this review. Five studies only included participants with pneumonia on imaging, suggesting that this is a highly selected population. In an additional four studies, we were unable to assess the risk for selection bias. These factors make it very difficult to determine the diagnostic properties of these signs and symptoms from the included studies. We also had concerns about the applicability of these results, since most studies included participants who were already admitted to hospital or presenting to hospital settings. This makes these findings less applicable to people presenting to primary care, who may have less severe illness and a lower prevalence of COVID-19 disease. None of the studies included any data on children, and only one focused specifically on older adults. We hope that future updates of this review will be able to provide more information about the diagnostic properties of signs and symptoms in different settings and age groups. AUTHORS' CONCLUSIONS The individual signs and symptoms included in this review appear to have very poor diagnostic properties, although this should be interpreted in the context of selection bias and heterogeneity between studies. Based on currently available data, neither absence nor presence of signs or symptoms are accurate enough to rule in or rule out disease. Prospective studies in an unselected population presenting to primary care or hospital outpatient settings, examining combinations of signs and symptoms to evaluate the syndromic presentation of COVID-19 disease, are urgently needed. Results from such studies could inform subsequent management decisions such as self-isolation or selecting patients for further diagnostic testing. We also need data on potentially more specific symptoms such as loss of sense of smell. Studies in older adults are especially important.

Title: CT imaging and clinical course of asymptomatic cases with COVID-19 pneumonia at admission in Wuhan, China Content: PURPOSE: Aimed to characterize the CT imaging and clinical course of asymptomatic cases with COVID-19 pneumonia. METHODS: Asymptomatic cases with COVID-19 pneumonia confirmed by SARS-COV-2 nucleic acid testing in Renmin Hospital of Wuhan University were retrospectively enrolled. The characteristics of CT imaging and clinical feature were collected and analyzed. RESULTS: 58 asymptomatic cases with COVID-19 pneumonia admitted to our hospital between Jan 1, 2020 and Feb 23, 2020 were enrolled. All patients had history of exposure to SARS-CoV-2. On admission, patients had no symptoms and laboratory findings were normal. The predominant feature of CT findings in this cohort was ground glass opacity (GGO) (55, 94.8%) with peripheral (44, 75.9%) distribution, unilateral location (34, 58.6%) and mostly involving one or two lobes (38, 65.5%), often accompanied by characteristic signs. After short-term follow-up, 16 patients (27.6%) presented symptoms with lower lymphocyte count and higher CRP, mainly including fever, cough and fatigue. The evolution of lesions on CT imaging were observed in 10 patients (17.2%). The average days of hospitalization was19.80±10.82 days, and was significantly longer in progression patients (28.60±7.55 day). CONCLUSION: CT imaging of asymptomatic cases with COVID-19 pneumonia has definite characteristics. Since asymptomatic infections as "covert transmitter", and some patients can progress rapidly in the short term. It is essential to pay attention to the surveillance of asymptomatic patients with COVID-19. CT scan has great value in screening and detecting patients with COVID-19 pneumonia, especially in the highly suspicious, asymptomatic cases with negative nucleic acid testing.

Title: Asymptomatic transmission during the COVID-19 pandemic and implications for public health strategies Content: SARS-CoV-2 spread rapidly within months despite global public health strategies to curb transmission by testing symptomatic patients and encouraging social distancing. Here, we summarize rapidly emerging evidence highlighting transmission by asymptomatic and pre-symptomatic individuals. Viral load of asymptomatic carriers is comparable to symptomatic patients, viral shedding is highest before symptom onset suggesting high transmissibility before symptoms. Within universally tested subgroups, surprisingly high percentages of COVID-19 positive asymptomatic individuals were found. Asymptomatic transmission was reported in several clusters. A Wuhan study showed an alarming rate of intrahospital transmission, and several countries reported higher prevalence among healthcare workers than the general population. This raises concern that health workers could act as silent disease vectors. Therefore, current public health strategies relying solely on 'symptom onset' for infection identification need urgent reassessment. Extensive universal testing irrespective of symptoms may be considered with priority placed on groups with high frequency exposure to positive patients.

Title: Presumed pulmonary COVID-19 infection detected incidentally on breast MR Content: COVID-19 is an infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). A global pandemic was declared by the World Health Organisation on 11 March 2020. Approximately 30% of infected individuals are asymptomatic.(1) We present the case of a 68-year-old female who underwent outpatient breast magnetic resonance (MR) imaging for assessment of a right breast mass. The study demonstrated abnormal subpleural high T2 signal intensity change within in the partially visualised lungs, which showed enhancement following administration of contrast. Concern was raised that the pulmonary changes may represent COVID-19 infection. The patient was urgently contacted and denied any current symptoms but reported suffering mild upper respiratory tract symptoms two weeks earlier. An outpatient chest radiograph demonstrated changes consistent with COVID-19 infection and the patient was treated as COVID-19 positive and advised to self-isolate for seven days as per Public Health England guidance.(2) Due to increasing breathlessness the patient presented to our Emergency Department the next day and underwent a CT pulmonary angiogram which demonstrated segmental pulmonary emboli and subpleural consolidation in keeping with COVID-19 infection. This represents the first case of COVID-19 identified on breast MR imaging that the authors have seen and highlights the importance of prompt identification and flagging of incidental pulmonary findings to minimise further transmission of the virus in asymptomatic carriers.

Title: Signs and symptoms to determine if a patient presenting in primary care or hospital outpatient settings has COVID-19 disease Content: BACKGROUND: Some people with SARS-CoV-2 infection remain asymptomatic, whilst in others the infection can cause mild to moderate COVID-19 disease and COVID-19 pneumonia, leading some patients to require intensive care support and, in some cases, to death, especially in older adults. Symptoms such as fever or cough, and signs such as oxygen saturation or lung auscultation findings, are the first and most readily available diagnostic information. Such information could be used to either rule out COVID-19 disease, or select patients for further diagnostic testing. OBJECTIVES: To assess the diagnostic accuracy of signs and symptoms to determine if a person presenting in primary care or to hospital outpatient settings, such as the emergency department or dedicated COVID-19 clinics, has COVID-19 disease or COVID-19 pneumonia. SEARCH METHODS: On 27 April 2020, we undertook electronic searches in the Cochrane COVID-19 Study Register and the University of Bern living search database, which is updated daily with published articles from PubMed and Embase and with preprints from medRxiv and bioRxiv. In addition, we checked repositories of COVID-19 publications. We did not apply any language restrictions. SELECTION CRITERIA: Studies were eligible if they included patients with suspected COVID-19 disease, or if they recruited known cases with COVID-19 disease and controls without COVID-19. Studies were eligible when they recruited patients presenting to primary care or hospital outpatient settings. Studies including patients who contracted SARS-CoV-2 infection while admitted to hospital were not eligible. The minimum eligible sample size of studies was 10 participants. All signs and symptoms were eligible for this review, including individual signs and symptoms or combinations. We accepted a range of reference standards including reverse transcription polymerase chain reaction (RT-PCR), clinical expertise, imaging, serology tests and World Health Organization (WHO) or other definitions of COVID-19. DATA COLLECTION AND ANALYSIS: Pairs of review authors independently selected all studies, at both title and abstract stage and full-text stage. They resolved any disagreements by discussion with a third review author. Two review authors independently extracted data and resolved disagreements by discussion with a third review author. Two review authors independently assessed risk of bias using the QUADAS-2 checklist. Analyses were descriptive, presenting sensitivity and specificity in paired forest plots, in ROC (receiver operating characteristic) space and in dumbbell plots. We did not attempt meta-analysis due to the small number of studies, heterogeneity across studies and the high risk of bias. MAIN RESULTS: We identified 16 studies including 7706 participants in total. Prevalence of COVID-19 disease varied from 5% to 38% with a median of 17%. There were no studies from primary care settings, although we did find seven studies in outpatient clinics (2172 participants), and four studies in the emergency department (1401 participants). We found data on 27 signs and symptoms, which fall into four different categories: systemic, respiratory, gastrointestinal and cardiovascular. No studies assessed combinations of different signs and symptoms and results were highly variable across studies. Most had very low sensitivity and high specificity; only six symptoms had a sensitivity of at least 50% in at least one study: cough, sore throat, fever, myalgia or arthralgia, fatigue, and headache. Of these, fever, myalgia or arthralgia, fatigue, and headache could be considered red flags (defined as having a positive likelihood ratio of at least 5) for COVID-19 as their specificity was above 90%, meaning that they substantially increase the likelihood of COVID-19 disease when present. Seven studies carried a high risk of bias for selection of participants because inclusion in the studies depended on the applicable testing and referral protocols, which included many of the signs and symptoms under study in this review. Five studies only included participants with pneumonia on imaging, suggesting that this is a highly selected population. In an additional four studies, we were unable to assess the risk for selection bias. These factors make it very difficult to determine the diagnostic properties of these signs and symptoms from the included studies. We also had concerns about the applicability of these results, since most studies included participants who were already admitted to hospital or presenting to hospital settings. This makes these findings less applicable to people presenting to primary care, who may have less severe illness and a lower prevalence of COVID-19 disease. None of the studies included any data on children, and only one focused specifically on older adults. We hope that future updates of this review will be able to provide more information about the diagnostic properties of signs and symptoms in different settings and age groups. AUTHORS' CONCLUSIONS: The individual signs and symptoms included in this review appear to have very poor diagnostic properties, although this should be interpreted in the context of selection bias and heterogeneity between studies. Based on currently available data, neither absence nor presence of signs or symptoms are accurate enough to rule in or rule out disease. Prospective studies in an unselected population presenting to primary care or hospital outpatient settings, examining combinations of signs and symptoms to evaluate the syndromic presentation of COVID-19 disease, are urgently needed. Results from such studies could inform subsequent management decisions such as self-isolation or selecting patients for further diagnostic testing. We also need data on potentially more specific symptoms such as loss of sense of smell. Studies in older adults are especially important.

Title: Asymptomatic transmission and the infection fatality risk for COVID-19: Implications for school reopening Content: Asymptomatic infection occurs for numerous respiratory viral diseases, including influenza and COVID-19. We seek to clarify confusion in three areas: age-specific risks of transmission and/or disease; various definitions for the COVID-19 “mortality rate”, each useful for specific purposes; and implications for student return strategies from pre-school through university settings.

Title: Low Transmission Risk of 9 Asymptomatic Carriers Tested Positive for both SARS-CoV-2 Nucleic Acid and Serum IgG Content: • Asymptomatic carriers (RT-PCR+ and serum IgG+) are unable to transmit virus. • Such a low transmission risk might be partly associated with high Ct values. • A new pattern in SARS-CoV-2 infected patients might have emerged.

Title: Asymptomatic transmission and the infection fatality risk for COVID-19: Implications for school reopening Content: Asymptomatic infection occurs for numerous respiratory viral diseases, including influenza and COVID-19. We seek to clarify confusion in three areas: age-specific risks of transmission and/or disease; various definitions for the COVID-19 "mortality rate", each useful for specific purposes; and implications for student return strategies from pre-school through university settings.

Title: Asymptomatic transmission during the COVID-19 pandemic and implications for public health strategies Content: SARS-CoV-2 spread rapidly within months despite global public health strategies to curb transmission by testing symptomatic patients and encouraging social distancing. Here, we summarize rapidly emerging evidence highlighting transmission by asymptomatic and pre-symptomatic individuals. Viral load of asymptomatic carriers is comparable to symptomatic patients, viral shedding is highest before symptom onset suggesting high transmissibility before symptoms. Within universally tested subgroups, surprisingly high percentages of COVID-19 positive asymptomatic individuals were found. Asymptomatic transmission was reported in several clusters. A Wuhan study showed an alarming rate of intrahospital transmission, and several countries reported higher prevalence among healthcare workers than the general population. This raises concern that health workers could act as silent disease vectors. Therefore, current public health strategies relying solely on ‘symptom onset’ for infection identification need urgent reassessment. Extensive universal testing irrespective of symptoms may be considered with priority placed on groups with high frequency exposure to positive patients.

Title: Epidemiological characterization of asymptomatic carriers of COVID-19 in Colombia Content: Objective: Asymptomatic carriers (AC) of the new Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) represent an important source of spread for Coronavirus Disease 2019 (COVID-19). Early diagnosis of these cases is a powerful tool to control the pandemic. Our objective was to characterize patients with AC status and identify associated sociodemographic factors. Methods: Using a cross-sectional design and the national database of daily occurrence of COVID-19, we characterized both socially and demographically all ACs. Additional Correspondence Analysis and Logistic Regression Model were performed to identify characteristics associated with AC state (OR, 95% CI). Results: 2338 ACs (11.8%; 95% CI, 11.3-12.2%) were identified, mainly in epidemiological week 18 [EW] (3.98; 3.24-4.90). Age [≤]39 years (1.56; 1.42-1.72). Male sex (1.39; 1.26-1.53), cases imported from Argentina, Spain, Peru, Brazil, Costa Rica or Mexico (3.37; 1.47-7.71) and autochthonous cases (4.35 ; 2.12-8.93) increased the risk of identifying AC. We also identified groups of departments with moderate (3.68; 3.13-4.33) and strong (8.31; 6.10-7.46) association with AC. Discussion: Sociodemographic characteristics strongly associated with AC were identified, which may explain its epidemiological relevance and usefulness to optimize mass screening strategies and prevent person-to-person transmission.

Title: Prevalence of positive COVID-19 among asymptomatic health care workers who care patients infected with the novel coronavirus: A retrospective study Content: BACKGROUND: Limited information is available about COVID-19 infections among health care workers. Sensitive detection of COVID-19 cases in health care workers is crucial for hospital infection prevention policy, particularly for those who work with vulnerable patients. The aim of this study is to describe the prevalence of positive COVID-19 among asymptomatic health care workers who took care of patients with COVID-19 during the pandemic. METHODS: This retrospective study included all health care workers at King Abdullah University Hospital who take care of patients infected with COVID-19 patients from March 18, 2020 to April 29, 2020. They were tested for COVID-19 infection by use of real-time reverse-transcriptase rRT-PCR on samples from nasopharyngeal swabs. RESULTS: A total number of 370 health care workers were screened. The majority were nurses followed by physicians and other personnel. This study showed that all asymptomatic health care workers were tested negative for COVID-19Q. CONCLUSION: Unexpectedly, the prevalence of positive COVID-19 among asymptomatic health care workers who take care of patients infected with the novel coronavirus was 0%. This result must be cautiously interpreted. Further studies are needed in order to find effective strategy of screening health care workers to insure a safe working environment.

Title: The relative transmissibility of asymptomatic COVID-19 infections among close contacts Content: Asymptomatic transmission of the coronavirus disease 2019 is an important topic. A recent study in China showed that transmissibility of the asymptomatic cases is comparable to that of symptomatic cases. Here, we discuss that the conclusion may depend on how we interpret the data. To the best of our knowledge, this is the first time the relative transmissibility of asymptomatic COVID-19 infections is quantified.

Title: Epidemiological and clinical features of asymptomatic patients with SARS‐CoV‐2 infection Content: Few studies reported the severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) infected patients with completely asymptomatic throughout the disease course. We investigated the epidemiological and clinical features of patients infected by SARS‐CoV‐2 without any symptoms. Patients with confirmed SARS‐CoV‐2 infection were retrospectively recruited. The demographic characteristics, clinical data, treatment, and outcomes of SARS‐CoV‐2 infected patients without any symptoms were analyzed. Fifteen (4.4%) of 342 SARS‐CoV‐2 infected patients did not develop any symptom during the course of the disease. The median time from exposure to diagnosis was 7.0 days (interquartile range [IQR]: 1.0‐15.0 days). Of the 15 patients, 14 patients were diagnosed by tested positive for SARS‐CoV‐2 in throat swabs, while one patient was only tested positive for SARS‐CoV‐2 in anal swabs. During hospitalization, only 1 (6.7%) patient developed lymphopenia. Abnormalities of chest computed tomography examinations were detected in 8 (53.4%) patients on admission. As of 8 March 2020, all patients have been discharged. The median time of SARS‐CoV‐2 tested negative from admission was 7.0 days (IQR: 4.0‐9.0 days). Patients without any symptoms but with SARS‐CoV‐2 exposure should be closely monitored and tested for SARS‐CoV‐2 both in anal and throat swabs to excluded the infection. Asymptomatic patients infected by SARS‐CoV‐2 have favorable outcomes.

Title: Asymptomatic COVID-19: What the Neuroradiologist Needs to Know about Pulmonary Manifestations Content: Coronavirus disease 2019 (COVID-19) is an infectious disease with a high asymptomatic incidence. Asymptomatic infections within a population will inevitably lead to diagnosis via unrelated medical imaging. We report the case of an asymptomatic patient undergoing a spine CT examination for trauma who was incidentally found to have lung abnormalities later confirmed to be COVID-19. We aim to familiarize neuroradiologists with the spectrum of COVID-19 pulmonary manifestations that are likely to be observed on neck and spine CT imaging.

Title: Asymptomatic COVID-19: What the Neuroradiologist Needs to Know about Pulmonary Manifestations. Content: Coronavirus disease 2019 (COVID-19) is an infectious disease with a high asymptomatic incidence. Asymptomatic infections within a population will inevitably lead to diagnosis via unrelated medical imaging. We report the case of an asymptomatic patient undergoing a spine CT examination for trauma who was incidentally found to have lung abnormalities later confirmed to be COVID-19. We aim to familiarize neuroradiologists with the spectrum of COVID-19 pulmonary manifestations that are likely to be observed on neck and spine CT imaging.

Title: Viral dynamics in asymptomatic patients with COVID-19 Content: Data are limited on the viral load, viral shedding patterns, and potential infectivity of asymptomatic patients (APs) with coronavirus disease 2019 (COVID-19). This study included 31 adult patients who were virologically confirmed to have COVID-19 but were asymptomatic on admission. Among these 31 patients, 22 presented symptoms after admission and were defined as asymptomatic patients in the incubation period (APIs); the other nine patients remained asymptomatic during hospitalization and were defined as asymptomatic patients (APs). The median cycle threshold (Ct) value of APs (39.0, interquartile range (IQR) 37.5-39.5) was significantly higher than that of APIs (34.5, IQR 32.2-37.0), indicating a lower viral load in APs. However, the duration of viral shedding remained similar in the two groups (7 days, IQR 5-14 days vs. 8 days, IQR 5-16 days). The study findings demonstrated that although APs with COVID-19 have a lower viral load, they still have certain period of viral shedding, which suggests the possibility of transmission during their asymptomatic period. Further longitudinal surveillance of these asymptomatic cases via virus nucleic acid testing are warranted.

Title: COVID-19 – What does a paediatrician need to know? Content: COVID-19 is a coronavirus responsible for a global pandemic that started in China in December 2019 and has quickly spread to almost all countries. Approximately 2% of cases are diagnosed in children. There is increasing evidence for transmission by asymptomatic or presymptomatic adults and children. The clinical features do not differ from those of other respiratory viral infections, although rare cases manifest an unusual rash involving the digits. Disease is generally mild in children but deaths have been reported. Risk groups for severe disease in children are yet to be delineated. All treatments remain experimental.

Title: CT imaging and clinical course of asymptomatic cases with COVID-19 pneumonia at admission in Wuhan, China Content: Abstract Purpose Aimed to characterize the CT imaging and clinical course of asymptomatic cases with COVID-19 pneumonia. Methods Asymptomatic cases with COVID-19 pneumonia confirmed by SARS-COV-2 nucleic acid testing in Renmin Hospital of Wuhan University were retrospectively enrolled. The characteristics of CT imaging and clinical feature were collected and analyzed. Results 58 asymptomatic cases with COVID-19 pneumonia admitted to our hospital between Jan 1, 2020 and Feb 23, 2020 were enrolled. All patients had history of exposure to SARS-CoV-2. On admission, patients had no symptoms and laboratory findings were normal. The predominant feature of CT findings in this cohort was ground glass opacity (GGO) (55, 94.8%) with peripheral (44, 75.9%) distribution, unilateral location (34, 58.6%) and mostly involving one or two lobes (38, 65.5%), often accompanied by characteristic signs. After short-term follow-up, 16 patients (27.6%) presented symptoms with lower lymphocyte count and higher CRP, mainly including fever, cough and fatigue. The evolution of lesions on CT imaging were observed in 10 patients (17.2%). The average days of hospitalization was19.80±10.82 days, and was significantly longer in progression patients (28.60±7.55 day). Conclusion CT imaging of asymptomatic cases with COVID-19 pneumonia has definite characteristics. Since asymptomatic infections as “covert transmitter”, and some patients can progress rapidly in the short term. It is essential to pay attention to the surveillance of asymptomatic patients with COVID-19. CT scan has great value in screening and detecting patients with COVID-19 pneumonia, especially in the highly suspicious, asymptomatic cases with negative nucleic acid testing.

Title: COVID-19: asymptomatic carrier transmission is an underestimated problem Content: At the present time, COVID-19 is spreading rapidly [1]. The global prevention and control of COVID-19 is focused on the estimation of the relevant incubation period, basic reproduction number (R(0)), effective reproduction number (R(t)) and death risk. Although the prevention and control of COVID-19 requires a reliable estimation of the relevant incubation period, R(0), R(t) and death risk. Another key epidemiological parameter-asymptomatic ratio that provides strength and range for social alienation strategies of COVID-19, which is widely defined as the proportion of asymptomatic infections among all disease infections. In fact, the ratio of asymptomatic infection is a useful indicator of the burden of disease and a better measurement of the transmissibility of the virus. So far, people have not paid enough attention to asymptomatic carriers. The asymptomatic carriers discussed in this study are recessive infections, that is, those who have never shown symptoms after onset of infection. We will discuss three aspects: detection, infectivity and proportion of healthy carriers.

Title: Lung Involvement Found on Chest CT Scan in a Pre-Symptomatic Person with SARS-CoV-2 Infection: A Case Report Content: The novel coronavirus SARS-CoV-2 infection is spreading worldwide, and there are many reports of acute respiratory distress syndrome caused by this infection. However, asymptomatic lung involvement has not been reported. We hereby present the case of a 44-year-old health-care worker, who was found to be infected with the SARS-CoV-2 virus after a CT-scan performed for an unrelated condition revealed a lesion in the lung field compatible with COVID-19 infection. His condition deteriorated initially, but eventually improved with supportive treatment and the compassionate use of antivirals and antimalarials and is now in a stable condition.

Title: Diagnóstico De Neumonía Covid 19 En Pacientes Asintomáticos Tras La Realización De Un Pet-tc Oncológico Content: INTRODUCTION: On January 30, 2020, the World Health Organization (WHO) declared an international emergency due to the pandemic caused by a new coronavirus. There are some oncological indications that have special priority and studies are still being carried out despite the current situation. In these studies we have found suspicious findings of COVID-19 pneumonia in asymptomatic patients. The objective of this work is to assess the incidence of these findings, describe their characteristics and the evolution of suspected patients. MATERIAL AND METHODS: Oncological PET studies carried out in asymptomatic patients between March 18 and April 8, 2020 have been reviewed. Patients who presented findings suggestive of corresponding to an pulmonary infectious process were selected. Clinical findings have been reviewed to confirm or rule out SARS-CoV2 infection. RESULTS: During the specified period, a total of 129 PET-CT studies were performed. Of these, 11 (8.5%) found suspicious findings of a pulmonary infectious process. These were 8 men and 3 women aged between 30 and 79 years (mean 62.2). CONCLUSIONS: Patients with COVID 19 can present few symptoms of the disease, and in PET-CT studies both presymptomatic and almost asymptomatic patients can be detected, so nuclear medicine physicians should take special attention to the pulmonary evaluation of PET-CT studies.

Title: Rapid asymptomatic transmission of COVID-19 during the incubation period demonstrating strong infectivity in a cluster of youngsters aged 16-23 years outside Wuhan and characteristics of young patients with COVID-19: A prospective contact-tracing study Content: Summary Background The outbreak of coronavirus-disease-2019 (COVID-19) has rapidly spread to many places outside Wuhan. Previous studies on COVID-19 mostly included older hospitalized-adults. Little information on infectivity among and characteristics of youngsters with COVID-19 is available. Methods A cluster of 22 close-contacts of a 22-year-old male (Patient-Index) including youngsters with laboratory-confirmed COVID-19 and hospitalized close-contacts testing negative for severe-acute-respiratory-syndrome-coronavirus-2 (SARS-CoV-2) in Anhui Province, China was prospectively-traced. Results Since January 23, 2020, we enrolled a cluster of eight youngsters with COVID-19 (median age [range], 22 [16–23] years; six males) originating from Patient-Index returning from Wuhan to Hefei on January 19. Patient-Index visited his 16-year-old female cousin in the evening on his return, and met 15 previous classmates in a get-together on January 21. He reported being totally asymptomatic and were described by all his contacts as healthy on January 19-21. His very first symptoms were itchy eyes and fever developed at noon and in the afternoon on January 22, respectively. Seven youngsters (his cousin and six classmates) became infected with COVID-19 after a-few-hour-contact with Patient-Index. None of the patients and contacts had visited Wuhan (except Patient-Index), or had any exposure to wet-markets, wild-animals, or medical-institutes within three months. For affected youngsters, the median incubation-period was 2 days (range, 1–4). The median serial-interval was 1 day (range, 0–4). Half or more of the eight COVID-19-infected youngsters had fever, cough, sputum production, nasal congestion, and fatigue on admission. All patients had mild conditions. Six patients developed pneumonia (all mild; one bilateral) on admission. As of February 20, four patients were discharged. Conclusions SARS-CoV-2-infection presented strong infectivity during the incubation-period with rapid transmission in this cluster of youngsters outside Wuhan. COVID-19 developed in these youngsters had fast onset and various nonspecific atypical manifestations, and were much milder than in older patients as previously reported.

Title: DIAGNÓSTICO DE NEUMONÍA COVID 19 EN PACIENTES ASINTOMÁTICOS TRAS LA REALIZACIÓN DE UN PET-TC ONCOLÓGICO Content: ABSTRACT INTRODUCTION: On January 30, 2020, the World Health Organization (WHO) declared an international emergency due to the pandemic caused by a new coronavirus. There are some oncological indications that have special priority and studies are still being carried out despite the current situation. In these studies we have found suspicious findings of COVID-19 pneumonia in asymptomatic patients. The objective of this work is to assess the incidence of these findings, describe their characteristics and the evolution of suspected patients. MATERIAL AND METHODS: Oncological PET studies carried out in asymptomatic patients between March 18 and April 8, 2020 have been reviewed. Patients who presented findings suggestive of corresponding to an pulmonary infectious process were selected. Clinical findings have been reviewed to confirm or rule out SARS-CoV2 infection. RESULTS: During the specified period, a total of 129 PET-CT studies were performed. Of these, 11 (8.5%) found suspicious findings of a pulmonary infectious process. These were 8 men and 3 women aged between 30 and 79 years (mean 62.2). CONCLUSIONS: Patients with COVID 19 can present few symptoms of the disease, and in PET-CT studies both presymptomatic and almost asymptomatic patients can be detected, so nuclear medicine physicians should take special attention to the pulmonary evaluation of PET-CT studies.

Title: Early viral clearance and antibody kinetics of COVID-19 among asymptomatic carriers Content: Background Asymptomatic carriers contribute to the spread of Coronavirus Disease 2019 (COVID-19), but their clinical characteristics, viral kinetics, and antibody responses remain unclear. Methods A total of 56 COVID-19 patients without symptoms at admission and 19 age-matched symptomatic patients were enrolled. RNA of SARS-CoV-2 was tested using transcriptase quantitative PCR, and the total antibodies (Ab), IgG, IgA and IgM against the SARS-CoV-2 were tested using Chemiluminescence Microparticle Immuno Assay. Results Among 56 patients without symptoms at admission, 33 cases displayed symptoms and 23 remained asymptomatic throughout the follow-up period. 43.8% of the asymptomatic carriers were children and none of the asymptomatic cases had recognizable changes in C-reactive protein or interleukin-6, except one 64-year-old patient. The initial threshold cycle value of nasopharyngeal SARS-CoV-2 in asymptomatic carriers was similar to that in pre-symptomatic and symptomatic patients, but the communicable period of asymptomatic carriers (9.63 days) was shorter than pre-symptomatic patients (13.6 days). There was no obvious differences of the seropositive conversion rate of total Ab, IgG, and IgA among the three groups, though the rates of IgM varied largely. The average peak IgG and IgM COI of asymptomatic cases was 3.5 and 0.8, respectively, which is also lower than those in symptomatic patients with peaked IgG and IgM COI of 4.5 and 2.4 (p <0.05). Conclusion Young COVID-19 patients seem to be asymptomatic cases with early clearance of SARS-CoV-2 and low levels of IgM generation but high total Ab, IgG and IgA. Our findings provide empirical information for viral clearance and antibody kinetics of asymptomatic COVID-19 patients.

Title: Prevalence of SARS-CoV-2 infection among asymptomatic healthcare workers in greater Houston: a cross-sectional analysis of surveillance data from a large healthcare system Content: Objective: To determine the prevalence of SARS-CoV-2 infection among asymptomatic COVID-19 facing and non-COVID-19 facing Healthcare Workers (HCWs), with varying job categories across different hospitals. Design: Cross-sectional analysis of a healthcare system surveillance program that included asymptomatic clinical (COVID-19 facing and non-COVID-19 facing), and non-clinical HCWs. A convenience sample of asymptomatic community residents (CR) was also tested. Proportions and 95% confidence intervals (CI) of SARS-CoV-2 positive HCWs are reported. Proportional trend across HCW categories was tested using Chi Square trend test. Logistic regression model-based likelihood estimates of SARS-CoV-2 prevalence among HCWs with varying job functions and across different hospitals are reported as adjusted odds ratios (aOR) and CI. Setting: Healthcare system comprising one tertiary care academic medical center and six large community hospitals across Greater Houston and a community sample. Participants: 2,872 self-reported asymptomatic adult (> 18 years) HCWs and CRs. Exposure: Clinical HCWs in COVID-19 and non-COVID-19 units, non-Clinical HCWs, and CRs. Job categories of Nursing, Providers, Allied Health, Support, and Administration / Research. Seven hospitals in the healthcare system. Main Outcomes: Positive reverse transcriptase polymerized chain reaction (RT-PCR) test for SARS-CoV-2 Results: Among 2,872 asymptomatic HCWs and CRs, 3.9% (CI: 3.2 - 4.7) tested positive for SARS-CoV-2. Mean (SD) age was 40.9 (11.7) years and 73% were females. Among COVID-19 facing HCWs 5.4% (CI: 4.5 - 6.5) were positive, whereas 0.6% (CI: 0.2 - 1.7%) of non COVID-19 facing HCWs and none of the non-clinical HCWs or CRs were positive (Ptrend < 0.001). Among COVID-19 facing HCWs, SARS-CoV-2 positivity was similar for all job categories (p = 0.74). However, significant differences in positivity were observed across hospitals. Conclusions and Relevance: Asymptomatic HCWs with COVID-19 patient exposure had a higher rate of SARS-CoV-2 positive testing than those not routinely exposed to COVID-19 patients and those not engaged in patient care. Among HCWs with routine COVID-19 exposure, all job types had relatively similar infection rates. These data can inform hospital surveillance and infection control practices for patient-facing job classifications and suggest that general environmental exposure within hospitals is not a significant source of asymptomatic SARS-CoV-2 infection.

Title: Estimating the Asymptomatic Proportion of 2019 Novel Coronavirus onboard the Princess Cruises Ship, 2020 Content: The potential infectiousness of asymptomatic COVID-19 cases together with a substantial fraction of asymptomatic infections among all infections, have been highlighted in clinical studies. We conducted statistical modeling analysis to derive the delay-adjusted asymptomatic proportion of the positive COVID-19 infections onboard the Princess Cruises ship along with the timeline of infections. We estimated the asymptomatic proportion at 17.9% (95% CrI: 15.5%-20.2%), with most of the infections occurring before the start of the 2-week quarantine.

Title: The proportion of COVID-19 cases that are asymptomatic in South Korea: Comment on Nishiura et al Content: The Korean Centers for Disease Control & Prevention reports the asymptomatic case proportion for COVID-19 is 33.3%. The asymptomatic case proportion in South Korea closely approximates the rate of 30.8% reported by Nishiura et al. (2020) among Japanese nationals returning from abroad.

Title: Asymptomatic cases with SARS-CoV-2 infection Content: On 31 March 2020, Chinese Health Authorization announced that numbers of asymptomatic cases with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection will be made to the public daily. This was a very important step since different counties have different capacities for the detection of SARS-CoV-2 infection and control strategy for the Coronavirus Disease 2019 outbreak. We summarized the characteristics of asymptomatic SARS-CoV-2 infections and the transmission potential of asymptomatic cases. Then we provided guidelines for the management of asymptomatic cases through quarantine and nucleic acid/serology tests.

Title: A COVID-19 Transmission within a family cluster by presymptomatic infectors in China Content: We report a COVID-19 family cluster caused by a presymptomatic case. There were 9 family members, including 8 laboratory-confirmed with COVID-19, and a 6-year-old child had no evidence of infection. Amongst the 8 patients, one adult and one 13-month-old infant were asymptomatic, one adult was diagnosed as having severe pneumonia.

Title: Clinical features of covid-19 in children Content: In early December, pneumonia cases of unknown origin started to appear and, on the 7thof January 2020, these cases were declared to be caused by a novel beta-coronavirus according to viral genome sequencing on the 11thof February, 2020. Coronaviruses are enveloped, single strand RNA viruses that have been known to have the ability to mutate rapidly, alter tissue tropism and adjust to different epidemiological situations. As of the end of April 2020, 122,392 laboratory-confirmed cases of COVID-19 had been detected in Turkey, of whom 3,258 died. From the beginning of the COVID-19 epidemic, children seem to be less affected than adults. Therefore, there are limited data regarding the clinical features of COVID-19 in children. The majority of children with confirmed COVID-19 had a history of household contact. The most common symptoms were fever and cough. Previous data suggest that nearly half of patients are afebrile at the onset of the disease. Hospitalization and PICU admission rates for children were lower than for adults. However, PICU admission can be necessitated in children with severe disease. Infants, particularly under the age of 12 months, were more likely to develop severe disease. In children, milder and asymptomatic cases can be challenging and can play a role in transmission. In particular, clinicians should test those children who have a history of family cluster even though they are asymptomatic or present with mild symptoms.

Title: SARS-CoV-2 infection in two patients following recent lung transplantation Content: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that causes Coronavirus disease 2019 (COVID-19) has become a world spreading health problem with pandemic character. Lung transplant recipients may be particularly at risk due to the high degree of immunosupression and the lung being the organ primarily affected by COVID-19. We describe a 16-year old male and a 64-year old female recently lung transplanted patients with COVID-19 during inpatient rehabilitation. Both patients were on triple immunosuppressive therapy and had no signs of allograft dysfunction. Both patients had close contact to a person who developed COVID-19 and were tested positive for SARS-CoV-2. Subsequently, both patients underwent systematic screening and SARS-CoV-2 was detected ultimately. While the 16-year old boy was completely asymptomatic, the 64-year old woman developed only mild COVID-19. Immunosuppressive therapy was unchanged and no experimental treatment was initiated. No signs of graft involvement or dysfunction were noticed. In conclusion, our report of patients with asymptomatic SARS-CoV-2 infection and mild COVID-19 respectively, may indicate that lung transplant recipients are not per se at risk for severe COVID-19. Further observations and controlled trials are urgently needed to study SARS-CoV-2 infection in lung transplant recipients.

Title: The role of asymptomatic SARS-CoV-2 infections: rapid living systematic review and meta-analysis Content: Background: There is substantial disagreement about the level of asymptomatic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in a population. The disagreement results, in part, from the interpretation of studies that report a proportion of asymptomatic people with SARS-CoV-2 detected at a single point. Review questions: 1. Amongst people who become infected with SARS-CoV-2, what proportion does not experience symptoms at all during their infection? 2. Amongst people with SARS-CoV-2 infection who are asymptomatic when diagnosed, what proportion will develop symptoms later? 3. What proportion of SARS-CoV-2 transmission is accounted for by people who are either asymptomatic throughout infection, or pre-symptomatic? Methods: Rapid living systematic review (protocol https://osf.io/9ewys/). We searched Pubmed, Embase, bioRxiv and medRxiv using a living evidence database of SARS-CoV-2 literature on 25.03.2020. We included studies of people with SARS-CoV-2 diagnosed by reverse transcriptase PCR (RT-PCR) that documented follow-up and symptom status at the beginning and end of follow-up and modelling studies. Study selection, data extraction and bias assessment were done by one reviewer and verified by a second, with disagreement resolved by discussion or a third reviewer. We used a common-effect model to synthesise proportions from comparable studies. Results: We screened 89 studies and included 11. We estimated an upper bound for the proportion of asymptomatic SARS-CoV-2 infections of 29% (95% confidence interval 23 to 37%) in eight studies. Selection bias and likely publication bias affected the family case investigation studies. One statistical modelling study estimated the true proportion of asymptomatic infections at 18% (95% credibility interval 16 to 20%). Estimates of the proportions of pre-symptomatic individual in four studies were too heterogeneous to combine. In modelling studies, 40-60% of all SARS-CoV-2 infections are the result of transmission from pre-symptomatic individuals, with a smaller contribution from asymptomatic individuals. Conclusions: An intermediate contribution of pre-symptomatic and asymptomatic infections to overall SARS-CoV-2 transmission means that combination prevention, with enhanced hand and respiratory hygiene, testing tracing and isolation strategies and social distancing, will continue to be needed. The findings of this systematic review of publications early in the pandemic suggests that most SARS-CoV-2 infections are not asymptomatic throughout the course of infection.

Title: A Well Infant with Coronavirus Disease 2019 (COVID-19) with High Viral Load Content: A well 6-month-old infant with coronavirus disease 2019 (COVID-19) had persistently positive nasopharyngeal swabs to day 16 of admission. This case highlights the difficulties in establishing the true incidence of COVID-19 as asymptomatic individuals can excrete the virus. These patients may play important roles in human-to-human transmission in the community.

Title: Flash survey on severe acute respiratory syndrome coronavirus-2 infections in paediatric patients on anticancer treatment Content: INTRODUCTION: Since the beginning of COVID-19 pandemic, it is known that the severe course of the disease occurs mostly among the elderly, whereas it is rare among children and young adults. Comorbidities, in particular, diabetes and hypertension, clearly associated with age, besides obesity and smoke, are strongly associated with the need for intensive treatment and a dismal outcome. A weaker immunity of the elderly has been proposed as a possible explanation of this uneven age distribution. Thus, there is concern that children treated for cancer may allso be at risk for an unfavourable course of infection. Along the same line, anecdotal information from Wuhan, China, mentioned a severe course of COVID-19 in a child treated for leukaemia. AIM AND METHODS: We made a flash survey on COVID-19 incidence and severity among children on anticancer treatment. Respondents were asked by email to fill in a short Web-based survey. RESULTS: We received reports from 25 countries, where approximately 10,000 patients at risk are followed up. At the time of the survey, more than 200 of these children were tested, nine of whom were positive for COVID-19. Eight of the nine cases had asymptomatic to mild disease, and one was just diagnosed with COVID-19. We also discuss preventive measures that are in place or should be taken and treatment options in immunocompromised children with COVID-19. CONCLUSION: Thus, even children receiving anticancer chemotherapy may have a mild or asymptomatic course of COVID-19. While we should not underestimate the risk of developing a more severe course of COVID-19 than that observed here, the intensity of preventive measures should not cause delays or obstructions in oncological treatment.

Title: Comparison of transmissibility of coronavirus between symptomatic and asymptomatic patients: Reanalysis of the Ningbo Covid-19 data Content: We investigate the transmissibility of coronavirus for symptomatic and asymptomatic patients using the Ningbo Covid-19 data1. Through more in-depth and comprehensive statistical analysis, we conclude that there is no difference in the transmission rates of coronavirus between the symptomatic and asymptomatic patients, which is consistent with the original findings in Chen et al.1