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The evolution of COVID-19 epidemiology in North America
between March 01, 2020 and October 3, 2021 expressed as the number of confirmed
positive cases per 100000 of the population per Km2 of significant
population density area. In the USA (continental US only excluding Alaska
and Hawaii) and Canada only epidemiologically significant territory with
population density > 5-10 individuals / Km2 were included in the analysis.
Note that until February 2021 SARS-CoV-2 virus behaved as one panmictic
population unit throughout the entire continent regardless of non-pharmaceutical
intervention measures implemented in either country. The US epidemiology
changes from that of Canada only after the murder of George Floyd on May
25, 2020 due to Black Lives Matter organized protests, which resulted in
super-spreading events across the US. It was estimated that about 21 million
people attended these protests by mid June. This was reflected in the substantial
increase in incidence of reported COVID-19 cases.
About sixty percent of the US population became
exposed to the SARS-CoV-2 virus sometimes between the holidays and began
mounting its natural immune response to the pathogen. The observed dip
in reported cases after December 20, 2020 likely reflects the slow down
of COVID-19 testing between the holidays, however significant drop in the
US and Canadian COVID-19 incidence was observed on January 10, 2021 only
after the US population reached its herd immunity threshold for the strain
of the virus responsible for the US and Canadian second wave. Interestingly,
the COVID-19 incidence in Canada begins to follow the much larger US population
trend. Nevertheless, by May 16, 2021 only 35% of the Canadian population
was exposed to the virus suggesting that with its predominantly vulnerable
population Canada can expect more significant waves to come.
The Canadian COVID-19 incidence between March 22, 2020 and June 6,
2021 plotted together with its corresponding infection fatality ratio (IFR).
Notice the COVID-19 prevalent mortality gradually dropping throughout the
pandemic as the Canadian population continues its exposure to the virus
and begins mounting its immune response. At the beginning of the pandemic
the apparent COVID-19 mortalities appeared to be very high due to a number
of unrelated factors such as, the unfamiliarity with the novel disease
resulting in late diagnosis or misdiagnosis of COVID-19 cases, lack of
initial testing (this artificially diminished the equation denominator
resulting in large mortality value), in addition to some initial mishandling
of severe cases due to overwhelming of the medical system. This region
of the graph (blue dots) by no means reflects the true morbidity of COVID-19.
The Canadian IFR continues fluctuating below 0.2% while continually
dropping throughout the COVID-19 second wave.
The US COVID-19 incidence between March 22, 2020 and June 6, 2021 plotted
together with its corresponding infection fatality ratio (IFR). Like the
Canadian trend pictured above, the US COVID-19 prevalent mortality is seen
gradually dropping throughout the pandemic as the large US population continues
its exposure to the virus and begins mounting its natural immune response.
The US prevalent COVID-19 infection fatality ratio (IFR) remained fluctuating
around 0.16% throughout much of the pandemic with the exception of the
first wave, which was followed by the Black Lives Matter protests (blue
dots in the figure above). At the beginning of the pandemic the apparent
COVID-19 mortalities were very high likely due to a number of unrelated
factors such as, the unfamiliarity with the novel disease resulting in
late diagnosis or misdiagnosis of COVID-19 cases, lack of initial testing
in addition to some initial mishandling of severe cases due to overwhelming
of the medical system. This region of the graph (blue dots) by no means
reflects the true morbidity of COVID-19.
Data: WHO weekly reported SARS-CoV-2 virus
positive cases.
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