Heterogeneity in testing, diagnosis and outcome in SARS-CoV-2 infection across outbreak settings in the Greater Toronto Area, Canada: an observational study.

BACKGROUND: Congregate settings have been disproportionately affected by coronavirus disease 2019 (COVID-19) Our objective was to compare testing for, diagnosis of and death after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection across 3 settings (residents of long-term care homes, people living in shelters and the rest of the population) METHODS: We conducted a population-based prospective cohort study involving individuals tested for SARS-CoV-2 in the Greater Toronto Area between Jan 23, 2020, and May 20, 2020 We sourced person-level data from COVID-19 surveillance and reporting systems in Ontario We calculated cumulatively diagnosed cases per capita, proportion tested, proportion tested positive and case-fatality proportion for each setting We estimated the age- and sex-adjusted rate ratios associated with setting for test positivity and case fatality using quasi-Poisson regression RESULTS: Over the study period, a total of 173 092 individuals were tested for and 16 490 individuals were diagnosed with SARS-CoV-2 infection We observed a shift in the proportion of cumulative cases from all cases being related to travel to cases in residents of long-term care homes (20 4% [3368/16 490]), shelters (2 3% [372/16 490]), other congregate settings (20 9% [3446/16 490]) and community settings (35 4% [5834/16 490]), with cumulative travel-related cases at 4 1% (674/16490) Cumulatively, compared with the rest of the population, the diagnosed cases per capita was 64-fold and 19-fold higher among long-term care home and shelter residents, respectively By May 20, 2020, 76 3% (21 617/28 316) of long-term care home residents and 2 2% (150 077/6 808 890) of the rest of the population had been tested After adjusting for age and sex, residents of long-term care homes were 2 4 (95% confidence interval [CI] 2 2-2 7) times more likely to test positive, and those who received a diagnosis of COVID-19 were 1 4-fold (95% CI 1 1-1 8) more likely to die than the rest of the population INTERPRETATION: Long-term care homes and shelters had disproportionate diagnosed cases per capita, and residents of long-term care homes diagnosed with COVID-19 had higher case fatality than the rest of the population Heterogeneity across micro-epidemics among specific populations and settings may reflect underlying heterogeneity in transmission risks, necessitating setting-specific COVID-19 prevention and mitigation strategies