2023-05-12 14:14:10
According to a preliminary report published Thursday, May 11 by Public Health France (SPF), the 2022-2023 season will have been marked by an influenza epidemic “exceptional” in several ways. Firstly, by its precocity: the first outbreaks appeared at the end of November in Brittany and Normandy, before quickly spreading throughout the country. The peak was reached at the end of December, whereas it had come late in the previous season, at the beginning of spring.
How to explain it? Mainly by the weather. “We know that influenza viruses multiply more easily when it is cold, but the temperatures have cooled significantly since the end of October”, underlines Anne Goffard, virologist at the Lille University Hospital.
Exceptional, this epidemic was also exceptional in its duration: a wave of type B flu having taken over from a wave of flu A, the epidemic dragged on until the beginning of April, i.e. ten- nine weeks in all. “Certainly, it is not frequent but not unheard of, tempers Anne Goffard. We had somewhat equivalent epidemics in 2018 and 2019, both in terms of duration and severity. »
15-64 year olds particularly affected
Severity: this is another specificity of this flu season, from which the 15-64 year olds have particularly suffered. “As in 2018, the A (H3N2) virus is the one that circulated mainly; but we have noticed that it gives particularly severe pictures, especially among the youngest, reports Anne Goffard. For what reasons ? We don’t know yet. »
Among the 110,000 visits to the emergency room for influenza or influenza-like illness during the epidemic, 44% concerned 15-64 year olds, notes SPF. The latter also represented 23% of the 15,000 hospitalizations recorded over the season and half of the serious cases reported by the intensive care units.
“It reminds us that the flu can be severe or even very severe in anyone, even someone who is well,” pointe Anne Goffard, recalling that « 26% of people who went through intensive care had no risk factor for complications.
The epidemic was also more deadly than the previous one. Between the week of October 3, 2022 and that of April 24, 2023, 1,505 deaths due to influenza were recorded compared to 594 the previous season. Among them, 14 people were under the age of 15, 167 were between 15 and 64 years old and 1,324 were aged 65 or over.
Vaccination down
However, one piece of data should be reassuring, Anne Goffard raises: the effectiveness of vaccines. “Those we received in October were in line with the strains that circulated and made it possible to limit severe forms”, she says. According to SPF, 86% of people at risk who were admitted to intensive care were not vaccinated or had an “unspecified” vaccination status.
“No vaccine protects 100%, but for the flu as for the Covid, it remains an essential tool to avoid serious forms”, insists the virologist, worried about the decline in vaccination coverage in France. Of those at risk targeted for influenza vaccination, only 51.5% received an injection this year, compared to 52.6% the previous year. Far, far from the objective of the World Health Organization, set at 75%.
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