This text is taken from our newsletter “Le Courrier du coronavirus” of June 6, 2022. To subscribe, click here.
The rate of transmission of the circulating sub-variants is very difficult for scientists to establish, as these strains are constantly changing. A comparison of the contagiousness of the main strains is still dizzying.
The reproduction rates in the graph refer to R0, or the number of reinfections in an ideal environment, i.e. without a vaccine or confinement. Since this universe does not exist, mathematical models involving these artificial barriers make it possible to establish an average and a standard deviation. The index reproduced in the table is not precise, but gives “an order of magnitude”, specifies Mathieu Maheu-Giroux, specialist in the epidemiology of infectious diseases at McGill University.
This “ideal” rate also varies from country to country depending on the public health measures in place. “The R0 that we would measure during the summer would differ from the R0 that we would measure during the winter in Quebec. Even for the Wuhan strain, the R0 differs according to the populations”, explains Mr. Maheu-Giroux.
The real rate, Rt, is much lower, and the authorities have been trying for two years to keep it below 1, so that transmission slows down.
In Quebec, the Rt of the coronavirus has been below 1 since the beginning of April. However, it started to rise again at the beginning of May and is approaching the threshold where contamination is accelerating.
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