• Victoria Ng, Aamir Fazil, Lisa A Waddell, Christina Bancej, Patricia Turgeon, Ainsley Otten, Nicole Atchessi, and Nicholas H Ogden.
• Public Health Risk Sciences Division (Ng, Fazil, Waddell, Turgeon, Otten, Ogden), National Microbiology Laboratory, Infectious Disease Prevention and Control Branch, Public Health Agency of Canada, Guelph, Ont., and St. Hyacinthe, Que.; Centre for Immunization and Respiratory Infectious Diseases (Bancej), Infectious Disease Prevention and Control Branch, Public Health Agency of Canada, Ottawa, Ont.; Office of Biosecurity Programs and Planning (Atchessi), Centre for Biosecurity, Health Security Infrastructure Branch, Public Health Agency of Canada, Ottawa, Ont. victoria.ng@canada.ca.
• CMAJ. 2020 Sep 14; 192 (37): E1053E1064E1053-E1064.

BackgroundContinual efforts to eliminate community transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) will be needed to prevent additional waves of infection. We explored the impact of nonpharmaceutical interventions on projected SARS-CoV-2 transmission in Canada.MethodsWe developed an age-structured agent-based model of the Canadian population simulating the impact of current and projected levels of public health interventions on SARS-CoV-2 transmission. Interventions included case detection and isolation, contact tracing and quarantine, physical distancing and community closures, evaluated alone and in combination.ResultsWithout any interventions, 64.6% (95% credible interval [CrI] 63.9%-65.0%) of Canadians will be infected with SARS-CoV-2 (total attack rate) and 3.6% (95% CrI 2.4%-3.8%) of those infected and symptomatic will die. If case detection and contact tracing continued at baseline levels without maintained physical distancing and reimplementation of restrictive measures, this combination brought the total attack rate to 56.1% (95% CrI 0.05%-57.1%), but it dropped to 0.4% (95% CrI 0.03%-23.5%) with enhanced case detection and contact tracing. Combining the latter scenario with maintained physical distancing reduced the total attack rate to 0.2% (95% CrI 0.03%-1.7%) and was the only scenario that consistently kept hospital and intensive care unit bed use under capacity, prevented nearly all deaths and eliminated the epidemic. Extending school closures had minimal effects but did reduce transmission in schools; however, extending closures of workplaces and mixed-age venues markedly reduced attack rates and usually or always eliminated the epidemic under any scenario.InterpretationControlling SARS-CoV-2 transmission will depend on enhancing and maintaining interventions at both the community and individual levels. Without such interventions, a resurgent epidemic will occur, with the risk of overwhelming our health care systems.© 2020 Joule Inc. or its licensors.

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