The flu epidemic, which is rapidly increasing in France, could have a "strong impact" on hospitals during the holidays, according to unprecedented projections from the Pasteur Institute and Public Health France, which have developed a new tool to inform health policy.
Just days before the Christmas school holidays, "the map of mainland France is completely red" for the flu: all regions, including Corsica, are experiencing an epidemic, observed Dr. Bruno Coignard, director of the infectious diseases department at SpF, during a press conference.
General practitioner consultations, emergency room visits, positive tests: the various health indicators related to influenza continue to increase.
Although the winter epidemic, so far mainly caused by type A viruses (H1N1 and H3N2), started a little early, the dynamics are so far similar to those of the previous seasons, 2023-2024 and 2022-2023, noted Dr. Coignard.
In France, the 2024/2025 season was particularly severe: more than 17,000 deaths, compared to an average of 9,000 to 10,000 usually, 30,000 hospitalizations and around a hundred "white plans", a system allowing operations to be rescheduled or staff to be recalled from leave.
Those over 65, pregnant women, immunocompromised individuals, and those with chronic illnesses remain at the highest risk of developing a severe form of the disease. Former Prime Minister François Bayrou, 74, was hospitalized in recent days with "a very severe case of the flu."
Across the Channel, the United Kingdom is facing an "unprecedented wave of super flu", according to the British public health service.
New this year in France: a modeling tool, developed by the Pasteur Institute and Public Health France and updated weekly, to help health authorities and caregivers anticipate the trajectory of the epidemic.
This combination of models provides scenarios on the dynamics of influenza circulation, at the national and regional level, over a four-week horizon, but also on the probable period of occurrence of the peak of the epidemic.
The first version "anticipates an increase in emergency room visits for flu-like symptoms" as Christmas approaches, before a decrease at the turn of the year, notably due to the delayed effect of a decrease in transmission linked to the closure of schools during the holidays, the two institutions summarized.
– “New tool” –
"The performance of the model can vary," noted Juliette Paireau, who works on the mathematical modeling of infectious diseases at the Pasteur Institute and SpF, during a press conference: "for seasons that resemble the past, the model performs best; for very different seasons, the model will have more difficulty anticipating the dynamics."
And this model does not take into account, for the moment, vaccination rates among people at risk of severe forms, nor the degree of effectiveness of the season's vaccine - which varies according to the dominant viral strains - nor the most circulating subtypes of virus.
"It's a new tool" and "it's part of our areas for improvement," said Simon Cauchemez, head of the modeling unit at the Pasteur Institute.
Given the forecasts and "despite the high degree of uncertainty inherent in modelling influenza activity", the two institutions have already warned of "a strong impact to be anticipated in hospitals during the end-of-year holiday period".
The peak of the flu epidemic is, at this stage, expected rather in the week of Christmas, with "15% chance that it will take place in week 51, 70% in week 52 and 12% in week 1", that of December 31, straddling the end of 2025 and the beginning of 2026.
But "great uncertainty" remains about its "scale", Juliette Paireau said.
At this stage, we cannot rule out a resurgence of the epidemic after the Christmas holidays, as in the 2023-2024 season, or later as in 2022-2023.
With the holidays approaching, which are conducive to gatherings, there is still time to get vaccinated and barrier gestures (masks, etc.) remain recommended, authorities insist, as Health Minister Stéphanie Rist said Wednesday evening on BFMTV.
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