Abstract
IntroductionThere is an evidence gap regarding the duration of SARS-CoV-2 shedding and of its variability across different care settings and by age, sex, income, and co-morbidities. Such evidence is part of understanding of infectivity and reinfection. We examine direct measures of viral shedding using a linked population-based health administrative dataset.MethodsLaboratory and sociodemographic databases for Ontario, Canada were linked to identify those testing positive (RT-PCR) between Jan. 15 and April 30, 2020 who underwent subsequent testing by May 31, 2020. To maximise use of available data, we computed two shedding duration estimates defined as the time between initial positive and most recent positive (documented shedding) or second of two negative tests (documented resolution). We also report multivariable results using quantile regression to examine subgroup differences.ResultsIn Ontario, of the 16,595 who tested positive before April 30, 2020, 6604 had sufficient subsequent testing to allow shedding duration calculation. Documented shedding median duration calculated in 4,889 (29% of 16,595) patients was 19 days (IQR 12–28). Documented resolution median duration calculated in 3,219 (19% of the 16,595) patients was 25 days (IQR 18–34). Long-term care residents had 3–5 day longer shedding durations using both definitions. Shorter documented shedding durations of 2–4 days were observed in those living in higher income neighbourhoods. Shorter documented resolution durations of 2–3 days were observed at the 25th% of the distribution in those aged 20–49. Only 11.5% of those with definitive negative test results reverted to negative status by day 14.ConclusionsViral shedding continued well beyond 14 days among this large subset of a population-based group with COVID-19, and longer still for long-term care residents and those living in less affluent neighborhoods. Our findings do not speak to duration of infectivity but are useful for understanding the expected duration of RT-PCR positivity and for identifying reinfection.
Highlights
There is an evidence gap regarding the duration of SARS-CoV-2 shedding and of its variability across different care settings and by age, sex, income, and co-morbidities
Viral shedding authors upon request, understanding that the computer programs may rely upon coding templates or macros that are unique to Institute for Clinical Evaluative Sciences (ICES) and are either inaccessible or may require modification
The data underlying the results presented in the study are available from the Institute for Clinical Evaluative Sciences (ICES) who can be contacted at https://www.ices.on.ca/AboutICES/ICES-Contacts-and-Sites/contact
Summary
There is an evidence gap regarding the duration of SARS-CoV-2 shedding and of its variability across different care settings and by age, sex, income, and co-morbidities. Subsequent research on molecular detection using real-time reverse transcriptase PCR (RT-PCR) suggested that SARS-CoV-2 shedding begins 2 to 3 days prior to symptom onset and continues for 7 to days [2,3,4,5,6,7,8,9], but for up to 20 to 31 days with more severe infection [4, 5, 10,11,12] This evidence lacked external validity as almost all studies had been conducted in single settings, and were limited to hospitalised patients. None of the studies referenced above were population-based and, with two exceptions [14, 15] they excluded censored cases (those that do not have a shedding resolution time)
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