Temporal estimates of case-fatality rate for COVID-19 outbreaks in Canada and the United States

1. Covid-19 case fatality estimated to be 1.6% in Canada and 1.8% in the USA

Evidence Rating: 2 (Good)

Covid-19 has disproportionately affected different areas of the world, not just in the number of cases, but also in the case-fatality rate (CFR): the percentage of deaths in comparison to the number of cases. For instance, estimated CFR values have varied from 0.4% in China to 31.4% in northwest Italy. But the estimation of CFR is confounded by two main factors. The first is the delay between contracting Covid-19 and death: When CFR is calculated at a certain point in time, the deaths resulting from currently active cases cannot be taken into account. The second factor is the underreporting of Covid-19 cases, due to lack of testing and asymptomatic individuals. This retrospective cohort study adjusted for these factors and estimated the CFR for Covid-19 in Canada and the USA, based on data on daily incidence of confirmed COVID-19 cases collected from Jan. 31 to Apr. 22, 2020. The CFR for Canada was 1.6% (95% credible interval of 0.7-3.1%) and the CFR for the USA was 1.8% (95% credible interval of 0.8-3.6%). These estimates are under the assumption that reporting rates for Covid-19 are under 50% in both countries. Overall, this principle of accounting for onset to death lag time and the underreporting of cases is important for future CFR estimates in specific regions, to provide a better understanding of the virulence of the SARS-CoV-2.

Click to read the study in CMAJ

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