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The natural history and transmission potential of asymptomatic SARS-CoV-2 infection.

ABSTRACT: 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.

SUBMITTER: Chau NVV

PROVIDER: S-EPMC7314145 | biostudies-literature | 2020 Jun

REPOSITORIES: biostudies-literature

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The Natural History and Transmission Potential of Asymptomatic Severe Acute Respiratory Syndrome Coronavirus 2 Infection.

Van Vinh Chau Nguyen N Lam Vo Thanh VT Dung Nguyen Thanh NT Yen Lam Minh LM Minh Ngo Ngoc Quang NNQ Hung Le Manh LM Ngoc Nghiem My NM Dung Nguyen Tri NT Man Dinh Nguyen Huy DNH Nguyet Lam Anh LA Nhat Le Thanh Hoang LTH Nhu Le Nguyen Truc LNT Ny Nguyen Thi Han NTH Hong Nguyen Thi Thu NTT Kestelyn Evelyne E Dung Nguyen Thi Phuong NTP Xuan Tran Chanh TC Hien Tran Tinh TT Phong Nguyen Thanh NT Tu Tran Nguyen Hoang TNH Geskus Ronald B RB Thanh Tran Tan TT Truong Nguyen Thanh NT Binh Nguyen Tan NT Thuong Tang Chi TC Thwaites Guy G Van Tan Le L

Clinical infectious diseases : an official publication of the Infectious Diseases Society of America 20201201 10

<h4>Background</h4>Little is known about the natural history of asymptomatic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection.<h4>Methods</h4>We conducted a prospective study at a quarantine center for coronavirus disease 2019 in Ho Chi Minh City, Vietnam. We enrolled quarantined people with reverse-transcription polymerase chain reaction (RT-PCR)-confirmed SARS-CoV-2 infection, collecting clinical data, travel and contact history, and saliva at enrollment and daily nasopha ...[more]

PMID: 32497212

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Project description:BackgroundHousehold transmission contributes to SARS-CoV-2 spread, but the role of children in transmission is unclear. We conducted a study that included symptomatic and asymptomatic children and adults exposed to SARS-CoV-2 in their households with the objective of determining how SARS-CoV-2 is transmitted within households.MethodsIn this case-ascertained antibody-surveillance study, we enrolled households in Ottawa, Ontario, in which at least 1 household member had tested positive for SARS-CoV-2 on reverse transcription polymerase chain reaction testing. The enrolment period was September 2020 to March 2021. Potentially eligible participants were identified if they had tested positive for SARS-CoV-2 at an academic emergency department or affiliated testing centre; people who learned about the study through the media could also self-identify for participation. At least 2 participants were required for a household to be eligible for study participation, and at least 1 enrolled participant per household had to be a child (age < 18 yr). Enzyme-linked immunosorbent assays were used to evaluate SARS-CoV-2-specific IgA, IgM and IgG against the spike-trimer and nucleocapsid protein. The primary outcome was household secondary attack rate, defined as the proportion of household contacts positive for SARS-CoV-2 antibody among the total number of household contacts participating in the study. We performed descriptive statistics at both the individual and household levels. To estimate and compare outcomes between patient subgroups, and to examine predictors of household transmission, we fitted a series of multivariable logistic regression with robust standard errors to account for clustering of individuals within households.ResultsWe enrolled 695 participants from 180 households: 180 index participants (74 children, 106 adults) and 515 of their household contacts (266 children, 249 adults). A total of 487 household contacts (94.6%) (246 children, 241 adults) had SARS-CoV-2 antibody testing, of whom 239 had a positive result (secondary attack rate 49.1%, 95% confidence interval [CI] 42.9%-55.3%). Eighty-eight (36.8%, 95% CI 29.3%-43.2%) of the 239 were asymptomatic; asymptomatic rates were similar for children (51/130 [39.2%, 95% CI 30.7%-48.5%]) and adults (37/115 [32.2%, 95% CI 24.2%-41.4%]) (odds ratio [OR] 1.3, 95% CI 0.8-2.1). Adults were more likely than children to transmit SARS-CoV-2 (OR 2.2, 95% CI 1.3-3.6). The odds of transmission from asymptomatic (OR 0.6, 95% CI 0.2-1.4) versus symptomatic (OR 0.9, 95% CI 0.6-1.4) index participants to household contacts was uncertain. Predictors of household transmission included household density (number of people per bedroom), relationship to index participant and number of cases in the household.InterpretationThe rate of SARS-CoV-2 transmission within households was nearly 50% during the study period, and children were an important source of spread. The findings suggest that children are an important driver of the COVID-19 pandemic; this should inform public health policy.

Project description:BackgroundReports suggest that asymptomatic individuals (those with no symptoms at all throughout infection) with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are infectious, but the extent of transmission based on symptom status requires further study.PurposeThis living review aims to critically appraise available data about secondary attack rates from people with asymptomatic, pre-symptomatic and symptomatic SARS-CoV-2 infection.Data sourcesMedline, EMBASE, China Academic Journals full-text database (CNKI), and pre-print servers were searched from 30 December 2019 to 3 July 2020 using relevant MESH terms.Study selectionStudies that report on contact tracing of index cases with SARS-CoV-2 infection in either English or Chinese were included.Data extractionTwo authors independently extracted data and assessed study quality and risk of bias. We calculated the secondary attack rate as the number of contacts with SARS-CoV-2, divided by the number of contacts tested.Data synthesisOf 927 studies identified, 80 were included. Summary secondary attack rate estimates were 1% (95% CI 0%-2%) with a prediction interval of 0%-10% for asymptomatic index cases in ten studies, 7% (95% CI 3%-11%) with a prediction interval of 1%-40% for pre-symptomatic cases in 11 studies and 6% (95% CI 5%-8%) with a prediction interval of 5%-38% for symptomatic index cases in 40 studies. The highest secondary attack rates were found in contacts who lived in the same household as the index case. Other activities associated with transmission were group activities such as sharing meals or playing board games with the index case, regardless of the disease status of the index case.LimitationsWe excluded some studies because the index case or number of contacts were unclear.ConclusionAsymptomatic patients can transmit SARS-CoV-2 to others, but our findings indicate that such individuals are responsible for fewer secondary infections than people with symptoms.Systematic review registrationPROSPERO CRD42020188168.

Project description:Background and Purpose Many of the statutes comprising the shelter-in-place and phased-reopening orders are centered around minimizing asymptomatic and presymptomatic transmission. Assumptions about the presence and relative importance of asymptomatic and presymptomatic transmission are based on case reports, the failing of quarantine measures aimed at sequestering ill patients, viral dynamic studies suggesting SARS-CoV-2 production peaks before symptoms appear, and modeling evidence that calculates serial interval between successive generations of infection. In aggregate, these data offer compelling evidence of asymptomatic and presymptomatic transmission, but individually these studies have notable shortcomings that undermine their conclusions. The purpose of this review is to discuss the literature of asymptomatic and presymptomatic transmission, highlight limitations of recent studies, and propose experiments that, if conducted, would provide a more definitive analysis of the relative role of asymptomatic and presymptomatic transmission in the ongoing SARS-CoV-2 pandemic. Methods We conducted a systematic review of literature on PubMed using search filters that relate to asymptomatic and presymptomatic transmission as well as serial interval and viral dynamics. We focused on studies that provided primary clinical data. Results 34 studies were eligible for inclusion in this systematic review: 11 case reports pertaining to asymptomatic transmission, 9 viral kinetic studies, 13 serial interval studies, and 1 study with viral kinetics and serial interval. Conclusion Different approaches to determining the presence and prevalence of asymptomatic and presymptomatic SARS-CoV-2 transmission have notable shortcomings, which were highlighted in this review and limit our ability to draw definitive conclusions. Conducting high quality studies with the aim of understanding the relative role of asymptomatic and presymptomatic transmission is instrumental to developing the most informed policies on reopening our cities, states, and countries.

Dataset Information

The natural history and transmission potential of asymptomatic SARS-CoV-2 infection.

Publications

The Natural History and Transmission Potential of Asymptomatic Severe Acute Respiratory Syndrome Coronavirus 2 Infection.

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