Establishment, contagiousness, and initial spread of SARS-CoV-2 in Canada
Martin Krkošek,
Madeline Jarvis-Cross,
Kiran Wadhawan,
Isha Berry,
Jean-Paul R. Soucy,
Korryn Bodner,
Ariel Greiner,
Leila Krichel,
Stephanie Penk,
Dylan Shea,
Juan S. Vargas Soto,
Ed W. Tekwa,
Nicole Mideo,
Péter K. Molnár
Affiliations
Martin Krkošek
Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON M5S 3B2, Canada
Madeline Jarvis-Cross
Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON M5S 3B2, Canada
Kiran Wadhawan
Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON M5S 3B2, Canada
Isha Berry
Division of Epidemiology, Dalla Lana School of Public Health, University of Toronto, Toronto, ON M5T 3M7, Canada
Jean-Paul R. Soucy
Division of Epidemiology, Dalla Lana School of Public Health, University of Toronto, Toronto, ON M5T 3M7, Canada
Korryn Bodner
Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON M5S 3B2, Canada Laboratory of Quantitative Global Change Ecology, Department of Biological Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto, ON M1C 1A4, Canada
Ariel Greiner
Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON M5S 3B2, Canada
Leila Krichel
Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON M5S 3B2, Canada
Stephanie Penk
Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON M5S 3B2, Canada Laboratory of Quantitative Global Change Ecology, Department of Biological Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto, ON M1C 1A4, Canada
Dylan Shea
Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON M5S 3B2, Canada
Juan S. Vargas Soto
Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON M5S 3B2, Canada Laboratory of Quantitative Global Change Ecology, Department of Biological Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto, ON M1C 1A4, Canada
Ed W. Tekwa
Department of Ecology, Evolution, and Natural Resources, Rutgers University, New Brunswick, NJ 08901-8551, USA
Nicole Mideo
Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON M5S 3B2, Canada
Péter K. Molnár
Laboratory of Quantitative Global Change Ecology, Department of Biological Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto, ON M1C 1A4, Canada
This study empirically quantifies dynamics of SARS-CoV-2 establishment and early spread in Canada. We developed a transmission model that was simulation tested and fitted in a Bayesian framework to timeseries of new cases per day prior to physical distancing interventions. A hierarchical version was fitted to all provinces simultaneously to obtain average estimates for Canada. Across scenarios of a latent period of 2–4 d and an infectious period of 5–9 d, the R0 estimate for Canada ranges from a minimum of 3.0 (95% CI: 2.3–3.9) to a maximum of 5.3 (95% CI: 3.9–7.1). Among provinces, the estimated commencement of community transmission ranged from 3 d before to 50 d after the first reported case and from 2 to 25 d before the first reports of community transmission. Among parameter scenarios and provinces, the median reduction in transmission needed to obtain R0 < 1 ranged from 46% (95% CI: 43%–48%) to 89% (95% CI: 88%–90%). Our results indicate that local epidemics of SARS-CoV-2 in Canada entail high levels of stochasticity, contagiousness, and observation delay, which facilitates rapid undetected spread and requires comprehensive testing and contact tracing for its containment.
