Viral kinetics of SARS-CoV-2 in asymptomatic carriers and presymptomatic patients
Seong Eun KimHae Seong JeongYohan YuSung Un ShinSoosung KimTae Hoon OhUh Jin KimSeung‐Ji KangHee‐Chang JangSook‐In JungKyung‐Hwa Park
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From a total of 71 laboratory-confirmed cases, three presymptomatic patients and 10 patients with entirely asymptomatic infections were identified. In two of the three incubation period patients, the viral titer in the presymptomatic period was very high (Ct value < 20). The median number of days to first negative RT-PCR in the asymptomatic carriers was 4.5 (range 2.5–9), and all asymptomatic carriers reached a first RT-PCR Ct > 35 within 14 days after diagnosis. Patients who have COVID-19 may already be infectious before there are symptoms, and 14 days of isolation after diagnosis may be sufficient in entirely asymptomatic cases.Keywords:
Asymptomatic carrier
Incubation period
2019-20 coronavirus outbreak
From a total of 71 laboratory-confirmed cases, three presymptomatic patients and 10 patients with entirely asymptomatic infections were identified. In two of the three incubation period patients, the viral titer in the presymptomatic period was very high (Ct value < 20). The median number of days to first negative RT-PCR in the asymptomatic carriers was 4.5 (range 2.5–9), and all asymptomatic carriers reached a first RT-PCR Ct > 35 within 14 days after diagnosis. Patients who have COVID-19 may already be infectious before there are symptoms, and 14 days of isolation after diagnosis may be sufficient in entirely asymptomatic cases.
Asymptomatic carrier
Incubation period
2019-20 coronavirus outbreak
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Wuhan is not only the first city to experience COVID-19 but is also among the first to emerge from the pandemic and currently has only 5 confirmed cases. The existence of asymptomatic carriers poses a threat for disease resurgence and also for virus transmission through transplantation. There are 2 types of asymptomatic carrier: the first is a recessive infection, with persistent but asymptomatic viral detection over 14 days or more, but with a relatively low-infectivity risk in the general community and unknown infection transmission risk from organ donation. The second group of asymptomatic cases are in the early stages of the incubation of the disease and become symptomatic over time but are contagious in the asymptomatic phase. To identify all asymptomatic carriers, Wuhan has carried out SARS-CoV-2 nucleic acid tests (NAT) for all city dwellers since May 14. As of May 24, 6 574 093 NAT tests have been completed, with a total of 227 new asymptomatic carriers and 1 new confirmed case.1 The asymptomatic infection rate in Wuhan has dropped from 0.5 per 1000 people2 to 0.03 per 1000 people. The outbreak of COVID-19 greatly slowed and then stopped organ donation and transplantation in Wuhan, but the decrease in the number of infections has allowed hospitals in Wuhan to carefully resume deceased donor organ donation and transplantation. Hyo-Lim Hong et al3 and Stephen Lagana et al4 have reported 2 cases of donor-derived transmission of COVID-19; therefore, a strategy is needed to prevent donor-derived transmission from all potential asymptomatic carriers. Because of the superficial understanding of COVID-19 and presence of asymptomatic infection in Wuhan, we instituted a protocol to prevent organ donor transmission of COVID-19. Before transplantation, both deceased donors and potential recipients undergo SARS-CoV-2 NAT and antibody tests as well as CT scans, which are repeated twice, to avoid the known false negative rates of single tests in COVID-19 patients and detect patients in the early stages of developing symptomatic disease. Donors and recipients must test negative twice to be eligible for transplant. To minimize transmission caused by asymptomatic carriers, potential deceased donors are quarantined in intensive care for >7 days while being tested. Suspected or confirmed COVID-19 patients would be eliminated from the donation process. From April 8, when Wuhan was reopened, to May 25, 43 cases of organ donation after brain death and 125 cases of organ transplant have been completed in Wuhan hospitals. There have been no cases of COVID-19 detected among organ transplant donors and recipients. This protocol may serve as a complex but necessary learning model for others.
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Background: Coronavirus disease 2019 (COVID-19) has been highly epidemic in the whole world now. Asymptomatic transmission of severe acute respiratory coronavirus-2 (SARS-CoV-2)might pose challenges for disease control. Little information on its characteristics of asymptomatic COVID-19 carriers is available. This study aimed to clarify the clinical feature and follow-up data of asymptomatic COVID-19 carriers, We hope the information would help the management of asymptomatic COVID-19 carriers. Methods: This retrospective study included all asymptomatic COVID-19 carriers inThe First People's Hospital of Yueyang(Hunan,China) and Hunan Provincial People's Hospital (Changsha, China) between January 22 and March 26, 2020. The epidemiology ,clinical characteristic,laboratory data,chest CT and follow-up data of these cases were investigated. Results: 24 asymptomatic COVID-19 carriers were enrolled inThe First People's Hospital of Yueyang and Hunan Provincial People's Hospital between Jan 22, 2020 and Mar 26, 2020 . All patients had history of exposure to SARS-CoV-2. During the whole disease course, patients had no symptoms and most of laboratory findings were normal. The median period from contact to diagnosis was 9.6days(1-38days). The median period from diagnosis to discharge was 14.4 days (6-24 days). Following after discharge,all patients continued to be asymptomatic.5(20.83%) patients were admitted again because their specimens(4 throat swab and 1 feces) showed re-positive results in SARS-CoV-2 PCR. The re-positive time away from diagnosis(day) was from 23-53 days; the time from re-positive to re-negative RT-PCR of SARS-CoV-2 was 3-11 days. Conclusion: Asymptomatic COVID-19 carriers have favorable outcomes and should be closely monitored. We suggested post-discharge surveillance of them.
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We read with interest the recent article by Yu et al, which reported asymptomatic transmission of coronavirus disease 2019 (COVID-19).1 Asymptomatic carriers of COVID-19 who have no clinical symptoms, but test positive for the virus that causes COVID-19 virus (SARS-CoV-2) in respiratory specimens or other specimens, have attracted the attention of scientists all over the world.2, 3 COVID-19 transmission through asymptomatic carriers has been a huge challenge for COVID-19 prevention and control.1 There are two types of asymptomatic carriers: those who never develop symptoms and those who are detected during the incubation period (pre-symptomatic detection) prior to symptom onset.3 Here, we discussed the identification and management of asymptomatic carriers of COVID-19 in China. So far, asymptomatic carriers of COVID-19 may be found by the following ways.3 First, close contacts of confirmed cases of COVID-19 may be identified as asymptomatic carriers during their medical observation period. Second, asymptomatic carriers have been found in the investigation of cluster outbreaks of COVID-19 by active detection. Third, asymptomatic infectors can be detected when tracing the potential infection sources of COVID-19 patients. Fourth, asymptomatic carriers may be detected in the screening populations with a history of travel or living in epidemic areas of COVID-19. Fifth, asymptomatic carriers could be detected during epidemiological investigations and opportunistic screening. Previous studies have reported asymptomatic transmission to family members4, 5 and described an example of asymptomatic transmission during the incubation period.6 Asymptomatic carriers can shed similar amounts of virus to symptomatic patients.7 Since April 1, 2020, the number of asymptomatic infectors has been reported online by National Health Commission of the People's Republic of China on a daily basis, and the following management measures were required to be carried out to minimize the risk of their transmission in China.3 First, persons detected as asymptomatic infectors would be isolated for 14 days, which may prevent them from becoming contagion sources. Those can be lifted from isolation by negative nucleic acid tests on two consecutive samples at least 24 hours apart.3 Second, epidemiological investigation of asymptomatic infectors would be strengthened, and strict disinfection would be implement in their living places such as homes, medical institutions, isolation wards, transport tools, and medical observation places. Third, since early detection of asymptomatic carriers is critical to contain their transmission, current screening methods also need to be strengthened. Nucleic acid screening is practical and quick for the population. However, due to specimen collection, testing methods, product stability, false-negative results have been frequently reported, which will hamper case detection and disease control.8 Therefore, multiple screening and monitoring of nucleic acid combining with antigens and antibodies in blood and other body fluids are recommended.8 At present, persons who are significant epidemiological associations with COVID-19 patients (eg, close contacts) will be put under 14-day centralized medical observation in China.3 As the epidemic enters a new stage, in order to consolidate the previous anti-epidemic achievements and prevent the epidemic from rebounding, we should further strengthen the monitoring of asymptomatic carriers and some special populations who may play a greater role in the spread of COVID-19, including front-line medical staff, disease control personnel, street epidemic prevention and control point staff, and delivery personnel. Since asymptomatic carriers have no clinical symptoms, they are difficult to identify, diagnose, and isolate. This can lead to loopholes in prevention and control measures, resulting in increased difficulty in controlling the spread of COVID-19.9 The public health education should be strengthened, and formation of good hygiene habits is important. In particular, awareness of self-protection, self-supervision and administration, and pre-service training of above special populations are critical to reducing the spread of asymptomatic infections. In future, further definition of high-risk populations and development of effective screening strategies and programs will support rapid identification and management of asymptomatic carrier transmission of COVID-19.9 Further study is needed on asymptomatic carriers including their frequency relative to symptomatic infections, their disease course, and factors associated with having an asymptomatic rather than symptomatic infection.8 Since there can be a gray area between asymptomatic and symptomatic infections, we also need to improve the detection of infections with very mild subclinical disease who may not seek medical attention but may also be responsible for transmission in the community. With so many scientific questions to be addressed in asymptomatic carriers of COVID-19, canceling public gatherings, implementing strong social-distancing measures, washing your hands, and wearing a mask may be the best way to stop the virus from spreading. In conclusion, asymptomatic carriers of COVID-19 can be contagious. Identification and management of these asymptomatic infectors has been strengthened in China. These measures may also help other countries to combat the COVID-19 epidemic. The authors declare that they have no competing interests. Jianhui Peng: Formal analysis; Writing-original draft; Writing-review & editing (equal). Dongwei Su: Formal analysis; Writing-original draft; Writing-review & editing (equal). Ziwei Zhang: Writing-review & editing (equal). Mingke Wang: Conceptualization (lead); Formal analysis (equal); Project administration (lead); Supervision (lead); Validation (lead); Writing-original draft (equal); Writing-review & editing (lead). The article does not contain the participation of any human being and animal.
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Asymptomatic carrier
2019-20 coronavirus outbreak
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Background: With the ongoing outbreak of COVID-19 around the world, it has become a worldwide health concern. Aim of study: check a cluster or presence of asymptomatic carrier with an asymptomatic transmission of COVID-19. Material m during Conclusions Infectivity of some asymptomatic SARS-CoV-2 carriers might be weak. Effective prevention and control measures are helpful to prevent COVID-19 spread of asymptomatic carriers. The result of this study may alleviate parts of the public concern about asymptomatic infected people further longitudinal surveillance of these asymptomatic cases via virus nucleic acid testing are warranted.
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2019-20 coronavirus outbreak
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In the current global coronavirus disease (COVID-19) pandemic, asymptomatic transmission of the causative agent, severe acute respiratory coronavirus-2 (SARS-CoV-2), poses a considerable challenge for disease control. Furthermore, information on the clinical characteristics of asymptomatic carriers is limited. Here, we aimed to clarify the clinical features and obtain follow-up data of asymptomatic carriers to assist in the clinical management of carriers. This retrospective study included all asymptomatic SARS-CoV-2 carriers diagnosed at the First People’s Hospital of Yueyang (Hunan, China) and Hunan Provincial People’s Hospital (Changsha, China) between January 22 and March 26, 2020. Data including the epidemiology, clinical characteristics, laboratory test results, and chest computed tomography status were collected, with a follow-up of these cases. A total of 24 asymptomatic carriers were enrolled at the First People’s Hospital of Yueyang and Hunan Provincial People’s Hospital between 22 January 2020 and 26 March 2020. All patients had previously been exposed to SARS-CoV-2. Over the monitored time, patients experienced no symptoms and most laboratory findings were normal. The median time from contact to diagnosis was 9.6 days (range: 1-38 days), while that from diagnosis to discharge was 14.4 days (range: 6-24 days). Following discharge, all patients remained asymptomatic. However, five patients (20.83%) were re-admitted because a polymerase chain reaction (PCR)-based re-test of their specimens (4 throat swabs and 1 feces) showed that they were positive for SARS-CoV-2. The time to re-testing positively varied from 23 to 53 days post-diagnosis. The time to re-testing negative for SARS-CoV-2 by real-time reverse transcription PCR after re-testing positive was 3 to 11 days. In conclusion, although asymptomatic carriers have favorable outcomes, they should be closely monitored. Also, clear guidelines need to be formulated and close surveillance is required for the management of asymptomatic carriers.
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Modified vaccinia Ankara
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Abstract Background: Previous studies have documented the clinical characteristics of patients with Coronavirus disease 2019(COVID-19) and presented evidence of person-to-person transmission. Limited data are available for patients with asymptomatic infections. Some asymptomatic carriers, whom we characterize as “exposers” or “infectors”, may be responsible for family clustering of COVID-19. Methods: A questionnaire survey and follow-up survey based on media reports were used to assess familial clustering of SARS-CoV-2 infection induced by asymptomatic exposers/infectors. Individual data were collected for all members of each tracked family. A transmission map was then drawn for each family. Results: Our study of 5 families indicated that individuals with no obvious symptoms of COVID-19, regardless of the PCR results, transmitted the virus to other family members who were community contained at home and had no contact with other infected individuals. There was one death case in Family No.3. Conclusion: Asymptomatic exposers/infectors of SARS-CoV-2 were all middle-aged (average age: 44.4 ± 14.9 years) who had no symptoms but had the ability to disseminate the virus. Medical staff participating in treatment of COVID-19 cases all had a high risk of infection, they should be quarantined so as to protect their families. The morbidity and mortality of Case 3.2 remind us that although these asymptomatic infected people have no symptoms, they are also infectious. It is not ruled out that the subsequent infected people are seriously ill or even die. Therefore, we should not take it lightly.
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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.
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