Flu Season Starts Early This Year

Flu activity picked up in September, roughly four to six weeks ahead of its usual pace, according to infectious disease doctors. The first increases appeared in California, Washington, Hawaii, and Alaska rather than the South. Nationally, 3.4% of people tested for a respiratory illness were positive for influenza, while overall levels remained low. Hawaii reported a 20.3% test-positivity rate, and California’s readings ranged from moderate to high depending on the area.

Doctors point to a changed H1N1 virus as one possible reason. The variant carries a G155E mutation in a place targeted by antibodies, and laboratory findings suggest existing antibodies may work less effectively, particularly among people born after the 2009 pandemic. Lower vaccination levels are not considered the explanation for the early timing, since many people have not yet been vaccinated at this point in the year.

The updated vaccine is available now at most major pharmacies and doctors’ offices. Doctors say it matches the strains currently circulating, although no flu shot prevents every infection. It is intended to lower the chances of serious outcomes, including hospitalization and death. The usual goal is vaccination by Halloween; protection takes about two weeks to develop, so the earlier activity has led doctors to say getting vaccinated now is reasonable, especially where cases are climbing. The early start does not predict the season’s ending or overall severity: later waves may involve H3N2 or influenza B, and the 2026–2027 season could still avoid being especially severe.