The virus is always circulating very intensely. The climate, the decline in immunity conferred by vaccines and the slightest remedy for barrier gestures could explain this resistance.
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If nowhere now does not wish to see, the SARS-COV-2 has not disappeared in France, far from it. “We are in a little particular period, with a long epidemic behind us but with a very intense circulation of the SARS-COV-2 virus,” said Laetitia Hurart, Scientific Director of Public Health France (SPF), Friday, April 15.
With nearly 135,000 new cases per day, the incidence remained at a very high level during the week of April 4-10 (week 14). At the national level, the incidence rate had stabilized at 1,406 cases per 100,000 population (- 2% compared to the previous week). Far away, if you think about it, the “alert threshold” of the 50 cases per 100,000 inhabitants of the beginning of the pandemic! This rate remained slightly in the 50 years and over, especially among 60-69 years (1,295, + 7%) and 70-79s (1,448, +6%). But it was sharply declining in 10-19 years (1,248, – 19%) and showed stable or slightly decrease in other age classes. The 30-39 age groups (1,690, – 1%) and 40-49 (1,721, – 4%) still had the highest rates. And the lowest rate (834) was observed in the under 10 years, probably immunized by the frequent infections of the months passed to school.
In early April, the different models of the Simon Cauchemez team, at the Institut Pasteur, provided a peak of incidence, for the epidemic rebound linked to BA.2, around the mid-April. Except that for about fifteen days, a curious plateau has settled in France – culminating again at a record level compared to other countries, according to the Ouwordindata website.
A fake dish, in reality, with “a small drop of a dozen days, followed by a three-day rise and then a new drop, but still moderate: it’s very odd “, notes Mahmoud Zureik, professor of epidemiology and public health at the University of Versailles-Saint-Quentin (Yvelines).
A underestimated incidence?
Reassuring point, between the 8th and 15th of April, this downward trend seems to have confirmed, indicates the epidemiologist. And the actual reproduction rate (“re”), which measures the number of people an infected individual goes on average contaminated, has been very close to the threshold of 1, meaning the next decline in the epidemic. Thursday, April 14, it was 1.01 – against 1.21 a week earlier.
Where does this “fall resistance impression”, according to Mahmoud Zureik, who have been observed for about fifteen days? Simon Cauchemez sees four possible assumptions. On the one hand, there was early April a wave of cold “quite surprising” because late and intense. “This cold has been able to slow down the decline in new infections; during past waves, the climate effect has already played.” Second explanation, the decline in immunity conferred by vaccination or by past infections. But the pastorian model used to predict the dynamics of wave BA.2 did not take into account this complex parameter. “This gradual decline in immunity can offer the virus a new fuel”, esteem Simon Cauchemez.
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