COVID-19 virus SARS-CoV-2

North American Wave 2 Epidemiology

The evolution of COVID-19 epidemiology in North America during the second wave of epidemic between August 2, 2020 and July 11, 2021. In both countries it is followed by a subsequent run up to the third wave at the end of summer, beginning of fall of 2021. Graphs are expressed as the number of official positive cases per 100000 of the population per Km2 of epidemiologically significant population density. About sixty percent of the US population became exposed to the virus by December 27, 2020 and began mounting its immune response to the pathogen. Due to the implementation of non-pharmaceutical interventions (NPIs) in Canada, this response was slowed substantially so that by December 27, 2020 only 15% of Canadians were exposed to the virus and began building their resilience to the COVID-19 disease. While the epidemiology of COVID-19 in North America clearly behaved as one panmictic virus population, notice the profound separation of the curves at the end of February 2021 apparently caused by the different level of herd immunity reached in each country. The implementation of NPIs in Canada clearly predisposed the Canadian population to subsequently higher vulnerability to the disease.

The COVID-19 incidence evolution during all three waves in Canada. The third wave of the epidemic is picking up in both countries by July/August 2021. In addition, the figure above depicts the Canadian infection fatality ratio (IFR) profile throughout the epidemic. In Canada the mean COVID-19 IFR throughout the 2021 stood at 0.13%. There was a noticeable up tick in the Canadian IFR at the end of June/beginning of August 2021. This is surprising as it coincides with a valley of low COVID-19 incidence. In addition to Canada, this identical increase in IFR was also noticed in Germany (not shown) and might be related to the government implemented vaccination program in both countries. In Canada vaccination program was associated with a 1.5 increase of disease severity (number of hospitalizations) in COVID-19 infected vaccinated persons together with doubling of mortalities. Data is updated as of August 15, 2021.

Data: WHO weekly reported SARS-CoV-2 virus positive cases.