As winter approaches, health officials on both sides of the english channel are monitoring a new influenza strain. A recently identified sub-clade of the A(H3N2) virus,dubbed K,is causing concern due to its rapid spread in the United Kingdom. While France has not yet experienced a surge linked to this variant, experts are carefully watching the situation following a especially challenging 2024-2025 flu season that saw over 17,000 excess deaths .
Each winter, influenza returns with a wave of fever, body aches, and work absences. This year, however, a slightly different guest is attracting attention: a sub-clade K of the A(H3N2) virus. The variant is receiving increased scrutiny in the United Kingdom, where health authorities have noted a faster and larger spread of H3N2 viruses, including this new subtype.
France is closely monitoring the situation across the English Channel. The key question is whether the genetic drift detected in the UK signals a more severe flu season domestically, or if France can avoid the worst of it.
Flu Epidemic: A Variant Gaining Ground in the UK
Table of Contents
First, it’s important to understand that the influenza virus is constantly changing. The K sub-clade isn’t a completely new virus, but rather a slightly different genetic branch of the typical H3N2 strain. The UK Health Security Agency (UKHSA) identified the increasing prevalence of this variant in British samples beginning in the fall. Agency reports indicate that A(H3N2), and particularly this sub-clade, currently dominates virological analyses in the country.
British media outlets, such as The Guardian, also report that the season started earlier than the previous year and that healthcare services are preparing for a higher-than-usual influx of patients. While this isn’t unusual in itself, the emergence of a slightly different virus version understandably raises concerns, especially during a period of strain on hospital capacity.
The U.S.-based Center for Infectious Disease Research and Policy (CIDRAP) clarifies that the K sub-clade represents a “drift” rather than a major break. It’s a genetic shift that can modestly reduce the recognition of the virus by existing immunity, but doesn’t represent the emergence of an entirely new subtype.
Flu: Questions About Vaccine Effectiveness
The UK has preliminary data from the UKHSA, dating from the fall, suggesting that current vaccines offer protection, including against severe illness, even if immune recognition appears slightly diminished based on several laboratory analyses. A decrease in efficacy doesn’t equate to a lack of protection. Even partial vaccination reduces the risk of hospitalization and complications.
In other words, the presence of the K sub-clade doesn’t render the vaccine useless. It simply suggests that protection may not be optimal, a common occurrence when the virus drifts more quickly than anticipated.
New Variant: Should France Be Concerned?
In France, the situation is different. As of today, no official reports describe this variant as dominant within the country. There are also no indications that the season is starting earlier due to the K sub-clade.
That doesn’t mean France is immune. Flu viruses circulate easily between countries, and it’s entirely possible that the K sub-clade will arrive in France in the coming weeks. However, it would be inaccurate to claim it’s already present on a massive scale.
The 2024-2025 season was one of the most challenging in recent years. According to Santé publique France, it began earlier than usual, lasted twelve weeks—longer than average—and was accompanied by an estimated excess of 17,000 deaths from all causes. The country is emerging from a taxing season, making the next one particularly closely watched.
Is There Cause for Alarm This Winter?
It would be an exaggeration to speak of an imminent threat. Available data doesn’t indicate that this sub-clade causes more severe illness than other H3N2 strains. What concerns British experts more is the combination of several factors:
In France, caution remains advised, but current information doesn’t support the conclusion of a catastrophic season. It’s known that the flu, especially when dominated by H3N2, can be particularly debilitating for the elderly and those with underlying health conditions. It’s also known that vaccination, even if imperfect, remains the best way to avoid hospitalization.
GOOD TO KNOW
In France, for the 2024-2025 season, the vaccination coverage rate for influenza is estimated at 46.5% among all people at risk of severe flu. Among these individuals, the rate reaches 53.7% for those aged 65 and older.
Subscribe to our newsletter
Ma Santé
