U.S. Flu Season Starts Early as CDC Reports 3.4% Positivity Rate
Updated
Updated · Livescience.com · Oct 13
U.S. Flu Season Starts Early as CDC Reports 3.4% Positivity Rate
3 articles · Updated · Livescience.com · Oct 13
Summary
CDC data for the week of Sept. 26 showed 3.4% of respiratory samples tested positive for flu, signaling the U.S. season is starting slightly earlier than usual.
That rate was about seven times higher than in the same week of 2025, with most early positive tests concentrated in Western states including California, Washington and Arizona.
Flu season typically begins in late October or early November and peaks between December and February, making the September uptick an earlier-than-normal shift.
Health officials still recommend annual vaccination in September or October for nearly everyone 6 months and older, with older adults able to choose high-dose, adjuvanted and new mRNA shots.