Countries across the globe are reporting an unusually early and intense start to flu season, driven by a newly mutated version of the H3N2 influenza A strain. This strain, which tends to cause more severe illness—especially in older adults and young children—picked up multiple mutations over the summer. Because of these changes, it differs from the H3N2 component included in this year’s flu vaccine.
The impact has been significant overseas:
- U.K.: Flu cases are already three times higher than this time last year, leading to a noticeable rise in hospitalizations.
- Japan: Experiencing an “unprecedented” early season, with infection levels nearly six times higher than last year.
- Canada: Also facing early activity, prompting national concern.
Experts say these trends are early signals of what could happen in the U.S. as flu season ramps up. The situation is made harder to monitor because the CDC’s influenza reporting was paused during the recent federal government shutdown. Although reporting will resume, it may take time to rebuild accurate, real-time data.
Additional challenges this season include:
- Lower flu vaccination rates, projected to drop by 12% overall—and even more among adults.
- Rising measles outbreaks, adding strain to public health systems.
- Disruptions to hospital-at-home programs, which many hospitals rely on to manage winter surges.
While this year’s flu shot is not a perfect match for the newly evolved H3N2 strain, experts still emphasize that vaccination remains one of the most effective tools to reduce severe illness, limit spread, and support hospital capacity.
Resource: Severe flu outbreaks across globe spur warnings for US