• Tara Kiran, Amy Craig-Neil, Paul Das, Joel Lockwood, Ri Wang, Nikki Nathanielsz, Esther Rosenthal, Carolyn Snider, and Stephen W Hwang.
• MAP Centre for Urban Health Solutions (Kiran, Craig-Neil, Wang, Snider, Hwang), and Department of Family and Community Medicine (Kiran, Das, Rosenthal), and Department of Emergency Medicine (Lockwood, Snider), and Department of Medicine (Hwang), St. Michael's Hospital, University of Toronto; Department of Family and Community Medicine (Kiran, Das, Rosenthal), and Institute of Health Policy, Management and Evaluation (Kiran, Snider), and Division of Emergency Medicine (Lockwood, Snider), and MD program (Nathanielsz), and Division of General Internal Medicine (Hwang), Department of Medicine, Faculty of Medicine, University of Toronto, Toronto, Ont. tara.kiran@utoronto.ca.
• CMAJ Open. 2021 Jan 1; 9 (1): E302-E308.

BackgroundIt is unclear what the best strategy is for detecting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) among residents of homeless shelters and what individual factors are associated with testing positive for the virus. We sought to evaluate factors associated with testing positive for SARS-CoV-2 among residents of homeless shelters and to evaluate positivity rates in shelters where testing was conducted in response to coronavirus disease 2019 (COVID-19) outbreaks or for surveillance.MethodsWe conducted a retrospective chart audit to obtain repeated cross-sectional data from outreach testing done at homeless shelters between Apr. 1 and July 31, 2020, in Toronto, Ontario, Canada. We compared the SARS-CoV-2 positivity rate for shelters where testing was conducted because of an outbreak (at least 1 known case) with those tested for surveillance (no known cases). A patient-level analysis evaluated differences in demographic, health and behavioural characteristics of residents who did and did not test positive for SARS-CoV-2 at shelters with at least 2 positive cases.ResultsOne thousand nasopharyngeal swabs were done on 872 unique residents at 20 shelter locations. Among the 504 tests done in outbreak settings, 69 (14%) were positive for SARS-CoV-2 and 1 (0.2%) was indeterminate. Among the 496 tests done for surveillance, 11 (2%) were positive and none were indeterminate. Shelter residents who tested positive for SARS-CoV-2 were significantly less likely to have a health insurance card (54% v. 72%, p = 0.03) or to have visited another shelter in the last 14 days (0% v. 18%, p < 0.01). There was no association between SARS-CoV-2 positivity and medical history or symptoms.InterpretationOur findings support testing of asymptomatic shelter residents for SARS-CoV-2 when a positive case is identified at the same shelter. Surveillance testing when there are no known positive cases may detect outbreaks, but further research should identify efficient strategies given scarce testing resources.© 2021 Joule Inc. or its licensors.

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