France is already plunged into a seasonal flu epidemic which leaves little respite. In its bulletin of December 10, Public Health France confirms that “influenza activity is increasing sharply in all age groups, in town and in hospitals, with a dynamic comparable to what was observed last year at the same period“To date, all regions, with the exception of Corsica, are in the epidemic phase.
Influenza 2025-2026: the epidemic is here, and it is ahead
This early start recalls an already known situation. “Like last year, we’re about four weeks early.”notes Bruno Lina, director of the National Reference Center (CNR) for respiratory viruses in Lyon in the Parisian.
Faced with this dynamic, scientists anticipate a “fairly tough season”, according to Marie-Anne Rameix Welti, director of the other CNR based at the Pasteur Institute in Paris, in the same article.
“Many factors make us fear a serious epidemic“, agrees Bruno Lina. An observation which is already reflected on the ground. The Bordeaux hospital has, for example, reintroduced the compulsory mask for caregivers and visitors.
The K variant, a new player in the H3N2 wave
After the Covid variants, it’s time for the flu! Derived from the A (H3N2) virus, the K variant is already actively circulating in England and Spain and should become the majority fairly quickly in France, according to experts.
“Coming from the A virus (H3N2), this more transmissible subclade could make the 2025-2026 season particularly serious”
adds Dr Gérald Kierzek.
It summarizes its likely impact. “This variant makes the flu more contagious thanks to mutations increasing its transmissibility and allowing partial immune escape, favoring an early start to the epidemic. And generally speaking, H3N2 is more severe than H1N1.”
A more contagious variant, which is transmitted more easily
If the K variant is worrying, it is above all because of its transmissibility. “It is not more severe, but it is more transmissible“, points out Bruno Lina. Scientists have identified three mutations which seem to allow it to enter our cells more easily.
Greater contagiousness means more people infected… and therefore potentially “more deaths at the end of the chain“, according to the virologist.
Dr. Gérald Kierzek nevertheless specifies that if it is not necessarily more serious in general, it affects older people more severely through prolonged intense fatigue and increased hospitalizations.
Should we be vaccinated despite potentially reduced effectiveness?
What about the vaccine, in these conditions? The threat of the K variant casts a shadow over the vaccination campaign, although it is increasing sharply (+17% of doses distributed compared to last year). Indeed, its manufacture took place in the spring, before the arrival and mutation of the K variant.
“We may fear lower vaccine effectiveness“, underlines Marie-Anne Rameix-Welti.
If its effectiveness against A viruses (H3N2) was only 30% last year (compared to 80% for type B), experts remain unanimous: it is not too late. So yes, get vaccinated, because a vaccine, even imperfect, slows viral progression and causes less serious forms of the disease.
“Vaccinate yourself against seasonal flu 2025-2026, even if the K variant was not exactly included during manufacturing: the effectiveness remains notable because although potentially “in the low range”, it will not be zero” assures Dr. Kierzek. “In addition, the arrival of two new reinforced vaccines this year (for seniors, more dosed or with an adjuvant) could partially offset this impact..
The comeback of barrier gestures
In the meantime, doctors and scientists insist on the need to apply other protective measures.
“Classic barrier measures are more relevant than ever: frequent hand washing, ventilation of premises, avoiding close contact if symptoms appear.
Regarding the mask, Dr. Kierzek is clear. “Wearing a mask is recommended in the event of flu symptoms, in crowded enclosed places, or to protect the vulnerable (hospitals, transport). It would effectively reduce airborne contagion, particularly with this highly transmissible variant.”