Covid-19, which has more than 95,000 confirmed cases and 3,200 deaths worldwide, presents as influenza-like illness. It is caused by a new SARS-CoV-2 coronavirus that appeared in Wuhan (China). If the flu is well known, many unknowns remain on SARS-CoV-2, especially since seasonal coronaviruses, which only cause common nasopharyngitis, are little studied. SARS-CoV seems to be transmitted more easily than influenza viruses and, above all, to cause more deaths among people affected, but the flu kills more people (up to 650,000 deaths per year) because it affects many more people. .
Professor Sylvie van Der Werf, head of the molecular genetics laboratory for RNA viruses and the national reference center for influenza viruses at the Pasteur Institute (Paris) analyzes the similarities and differences between these viruses and the diseases they cause . The world also drew on other sources, including information contained in the report of the joint mission, which was made up of 13 international experts chosen by WHO and 12 Chinese experts, who visited China from February 16 to 24.
Contagiousness
It is quantified by an estimate of the average number of people who contract the virus from an infected individual (what specialists call the basic reproduction rate or “R0”). This rate would be around 1.3 for influenza and 2.2 for SARS-CoV-2, which would therefore be more easily spread from one case. However, R0 is not a constant value and social distancing and quarantine measures have an impact on transmission.
The case fatality rate
According to data reported by the WHO-China mission and comments made by its leader, Dr. Bruce Aylward, the official figures for confirmed cases of Covid-19 in China are not far from the truth. This view is not unanimous and is important when calculating the fatality rate of an infectious disease, that is, the proportion of infected people who die. In the case of Covid-19, this ratio is 3.4% overall, with variations between 2 and 4%, depending on the region. An order of magnitude higher than that of influenza, which the WHO places below 1%. In France, seasonal flu affects between 2 million and 6 million people per year, with an average of 10,000 deaths per year, which would give a fatality rate ranging from 0.17% to 0.5%.
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