Mobile outreach testing for COVID-19 in twenty homeless shelters in Toronto, Canada
Abstract
Background
It is unclear what the best strategy is for detecting COVID-19 among homeless shelter residents and what individual factors are associated with positivity.
Methods
We conducted a retrospective chart audit obtaining repeated cross-sectional data from outreach testing done at homeless shelters between April 1 st and July 31 st , 2020 in Toronto, Canada. We compared the positivity rate for shelters tested because of an outbreak (at least one known case) versus surveillance (no known cases). A patient-level analysis examined differences in demographic, health, and behavioural characteristics of residents who did and did not test positive for COVID-19.
Findings
One 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 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 were significantly less likely to have a health insurance card (54% vs 72%, p=0.03) or have visited another shelter in the last 14 days (0% vs 18%, p<0.01) compared to those who tested negative; There was no association between COVID-19 positivity and medical history (p=0.40) or symptoms (p=0.43).
Interpretation
Our findings support testing of asymptomatic shelter residents for COVID-19 when a positive case is identified at the same shelter but suggest limited utility of testing all shelter residents in the absence of a known case. Visiting another shelter in the last 14 days is associated with a decreased risk of COVID-19 positivity.
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