Duration of SARS-CoV-2 shedding: A population-based, Canadian study

PLoS One. 2021 Jun 17;16(6):e0252217. doi: 10.1371/journal.pone.0252217. eCollection 2021.

Abstract

Introduction: 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. 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.

Methods: Laboratory 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.

Results: In 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.

Conclusions: Viral 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • COVID-19 / diagnosis*
  • COVID-19 / epidemiology
  • COVID-19 / virology
  • Epidemics / prevention & control
  • Female
  • Humans
  • Male
  • Middle Aged
  • Ontario / epidemiology
  • RNA, Viral / genetics
  • Reverse Transcriptase Polymerase Chain Reaction
  • SARS-CoV-2 / genetics*
  • SARS-CoV-2 / physiology
  • Time Factors
  • Virus Shedding / genetics*
  • Young Adult

Substances

  • RNA, Viral

Grants and funding

This work received no direct funding support. It was supported indirectly by ICES, which is funded by an annual grant from the Ontario Ministry of Health (MOH) and the Ministry of Long-Term Care (MLTC). One author (KS) was supported by an operating grant from the Canadian Institutes of Health Research (CIHR PJT 159516). JCK is supported by a Clinician Scientist Award from the University of Toronto Department of Family and Community Medicine. Parts of this material are based on data and/or information compiled and provided by the Canadian Institute for Health Information (CIHI). The analyses, conclusions, opinions, and statement expressed herein are those of the authors, and not necessarily those of CIHI. No endorsement by ICES, PHO, MOHLTC, or CIHI is intended or should be inferred nor did they have any role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. We thank IQVIA Solutions Canada Inc. for use of their Drug Information File. IQVIA Solutions Canada Inc. also had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.