Canada needs to rapidly escalate public health interventions for its COVID-19 mitigation strategies

Abstract

Background: After the declaration of COVID-19 pandemic on March 11th^, 2020, local transmission chains starting in different countries including Canada are forcing governments to take decisions on public health interventions to mitigate the spread of the epidemic.

Methods: We conduct data-driven and model-free estimations for the growth rates of the COVID-19 epidemics in Italy and Canada, by fitting an exponential curve to the daily reported cases. We use these estimates to predict epidemic trends in Canada under different scenarios of public health interventions.

Results: In Italy, the initial growth rate (0.22) has reduced to 0.1 two weeks after the lockdown of the country on March 8th^, 2020. This corresponds to an increase of the doubling time from about 3.15 to almost 7 days. In comparison, the growth rate in Canada has increased from 0.13 between March 1st and 13th, to 0.25 between March 13th to 22nd. This current growth rate corresponds to a doubling time of 2.7 days, and therefore, unless further public health interventions are escalated in Canada, we project 15,000 cases by March 31st. However, the case number may be reduced to 4000 if escalated public health interventions could instantly reduce the growth rate to 0.1, the same level achieved in Italy.

Interpretation: Prompt and farsighted interventions are critical to counteract the very rapid initial growth of the COVID-19 epidemic in Canada. Mitigation plans must take into account the delayed effect of interventions by up to 2-weeks and the short doubling time of 3-4 days.

Fig. 1

Linear regression of the logarithm of daily reported cases in Italy, Canada and the US. The estimated growth rate in Italy is 0.22 before March 8th, 0.14 between March 8th and March 12th, and 0.1 after March 12th. The estimated growth rate in Canada is 0.13 between March 1st and March 13th, and 0.25 after March 13th. The estimated growth rate in US is 0.3 between March 1st and March 21st.

Fig. 2

Left panel: reported cases in Italy (log scale), including total cumulative cases, cumulative deaths, daily hospitalizations and daily ICU. Right panel: proportions of daily hospitalizations over cumulative cases, cumulative deaths over cumulative cases, and daily ICU over hospitalizations.

Fig. 3

Predictions of the epidemic trend in Canada from March 21st: scenario with the estimated current growth rate of 0.25 (fitted between March 13th and 21st), and the growth rate of 0.1 estimated from Italy after closure of all non-essential activities. The projection for hospitalization numbers is based on the Italian data (daily hospitalizations are about 40% of the total number of detections).

Fig. 4

Top panel: exponential predictions with growth rates 0.25 and 0.1 applied to the Italian data, predicting from March 1st, 8th and 12th. Bottom panel: cumulative detected cases in Italy and Canada, with a time shift to compare the early growth.