The Natural History and Transmission Potential of Asymptomatic Severe Acute Respiratory Syndrome Coronavirus 2 Infection
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Abstract
Background
Little is known about the natural history of asymptomatic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection.
Methods
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 nasopharyngeal/throat swabs (NTSs) for RT-PCR testing. We compared the natural history and transmission potential of asymptomatic and symptomatic individuals.
Results
Between 10 March and 4 April 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. Seventeen (57%) participants imported cases. Compared with symptomatic individuals, asymptomatic people were less likely to have detectable SARS-CoV-2 in NTS collected at enrollment (8/13 [62%] vs 17/17 [100%]; P = .02). SARS-CoV-2 RNA was detected in 20 of 27 (74%) available saliva samples (7 of 11 [64%] in the asymptomatic group and 13 of 16 [81%] in the symptomatic group; P = .56). Analysis of RT-PCR positivity probability showed that asymptomatic participants had faster viral clearance than symptomatic participants (P < .001 for difference over the first 19 days). This difference was most pronounced during the first week of follow-up. Two of the asymptomatic individuals appeared to transmit SARS-CoV-2 to 4 contacts.
Conclusions
Asymptomatic SARS-CoV-2 infection is common and can be detected by analysis of saliva or NTSs. The NTS viral loads fall faster in asymptomatic individuals, but these individuals appear able to transmit the virus to others.
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SciScore for 10.1101/2020.04.27.20082347: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
Institutional Review Board Statement IRB: Apart from R, we also performed the analysis in SPSS V23.0 (IBM Corp, NY, US) and generated the figures using GraphPad PRISM® V5.04 (GraphPad Software Inc, CA, US) and R. Ethics: This clinical study received approvals from the Institutional Review Board of the HTD and the Oxford Tropical Research Ethics Committee of the University of Oxford.
Consent: Study participants gave their written informed consent.Randomization not detected. Blinding not detected. Power Analysis not detected. Sex as a biological variable not detected. Table 2: Resources
Software and Algorithms Sentences Resources Apart from R, we also performed the analysis in SPSS V23.0 (IBM Corp, NY, US) and … SciScore for 10.1101/2020.04.27.20082347: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
Institutional Review Board Statement IRB: Apart from R, we also performed the analysis in SPSS V23.0 (IBM Corp, NY, US) and generated the figures using GraphPad PRISM® V5.04 (GraphPad Software Inc, CA, US) and R. Ethics: This clinical study received approvals from the Institutional Review Board of the HTD and the Oxford Tropical Research Ethics Committee of the University of Oxford.
Consent: Study participants gave their written informed consent.Randomization not detected. Blinding not detected. Power Analysis not detected. Sex as a biological variable not detected. Table 2: Resources
Software and Algorithms Sentences Resources Apart from R, we also performed the analysis in SPSS V23.0 (IBM Corp, NY, US) and generated the figures using GraphPad PRISM® V5.04 (GraphPad Software Inc, CA, US) and R. Ethics: This clinical study received approvals from the Institutional Review Board of the HTD and the Oxford Tropical Research Ethics Committee of the University of Oxford. SPSSsuggested: (SPSS, RRID:SCR_002865)GraphPad PRISM®suggested: (GraphPad Prism, RRID:SCR_002798)GraphPadsuggested: (GraphPad Prism, RRID:SCR_002798)Results from OddPub: Thank you for sharing your code.
Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:Our study also has some limitations. We did not perform virus culture to demonstrate the infectiousness of SARS-CoV-2 detected by RT-PCR in saliva, although through contact history, we identified at least two transmission events from completely asymptomatic individuals. Additionally, we did not perform chest computerized tomography scans [24], which are more sensitive than chest radiographs for the detection of lung abnormalities. Therefore, we may have underestimated the sub-clinical findings of SARS-CoV-2 infection. Lastly, none of the participants developed severe disease. However, as of April 23, 2020, only three severe COVID-19 cases have been reported in HCMC and there have, as yet, been no COVID-19 related deaths in Vietnam. To summarize, we demonstrate that a high proportion (43%) of quarantined people who were RT-PCR positive for SARS-CoV-2 were asymptomatic. These individuals carried SARS-CoV- 2 in their respiratory tract and saliva, and were potentially contagious. They would not have been identified without the control measures as currently applied in Vietnam. Therefore, our findings emphasize the importance of contact tracing, airport quarantine and RT-PCR screening for SARS-CoV-2 among isolated people in controlling the ongoing pandemic.
Results from TrialIdentifier: No clinical trial numbers were referenced.
Results from Barzooka: We did not find any issues relating to the usage of bar graphs.
Results from JetFighter: We did not find any issues relating to colormaps.
Results from rtransparent:- Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
- Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
- No protocol registration statement was detected.
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