Flu season is off to an early start in some parts of the U.S., data shows. In a typical year, U.S. flu activity starts building in late fall — typically in October or November — and peaks between December and February. This year, flu activity is currently low but rising nationwide: During the week ending Sept. 26, 3.4% of respiratory samples tested by clinical labs were positive for flu, according to Centers for Disease Control and Prevention (CDC) data. That's about seven times the rate that was seen at the same point last year. About 0.5% of samples tested positive during the week ending Sept. 27, 2025."This particular year, it appears to be starting early — like right now," Dr. William Sc...