Abstract
This study aimed to investigate coronavirus disease (COVID-19) epidemiology in Alberta, British Columbia, and Ontario, Canada. Using data through December 1, 2020, we estimated time-varying reproduction number, Rt, using EpiEstim package in R, and calculated incidence rate ratios (IRR) across the 3 provinces. In Ontario, 76% (92 745/121 745) of cases were in Toronto, Peel, York, Ottawa, and Durham; in Alberta, 82% (49 878/61 169) in Calgary and Edmonton; in British Columbia, 90% (31 142/34 699) in Fraser and Vancouver Coastal. Across 3 provinces, Rt dropped to ≤ 1 after April. In Ontario, Rt would remain < 1 in April if congregate-setting-associated cases were excluded. Over summer, Rt maintained < 1 in Ontario, ~1 in British Columbia, and ~1 in Alberta, except early July when Rt was > 1. In all 3 provinces, Rt was > 1, reflecting surges in case count from September through November. Compared with British Columbia (684.2 cases per 100 000), Alberta (IRR = 2.0; 1399.3 cases per 100 000) and Ontario (IRR = 1.2; 835.8 cases per 100 000) had a higher cumulative case count per 100 000 population. Alberta and Ontario had a higher incidence rate than British Columbia, but Rt trajectories were similar across all 3 provinces.
Highlights
In 2020, the pandemic of the coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), spread across Canada
While the Canadian epidemic trajectory appeared to have stabilized over summer, the case count has surged since October, as seen in Figures 1–4 for Alberta, British Columbia, and Ontario
The dates of the first cases and the total number of cases in our data sets by each sub-provincial public health unit (PHU) in Alberta, British Columbia, and Ontario are presented in Supplementary Table S2
Summary
In 2020, the pandemic of the coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), spread across Canada. The first imported case was presented in a Toronto hospital on January 23, 2020.1,2 On March 13, Quebec was the first province to declare a public health emergency3; 4 days later, Alberta, British Columbia, and Ontario declared public health emergencies (Supplementary Table S1).[4] As of December 14, a cumulative total of 468 862 cases, including 13 553 deaths, has been reported in Canada.[5] While the Canadian epidemic trajectory appeared to have stabilized over summer, the case count has surged since October, as seen in Figures 1–4 for Alberta, British Columbia, and Ontario. Epidemiologists have explored various aspects of the pandemic in Canada, including data availability,[9] syndromic surveillance,[10] disease burden and mortality,[11] as well as the epidemiology in specific settings or subpopulations, such as nursing homes[12] and intensive care units.[13]
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