Seasonal influenza places a substantial burden on the U.S. healthcare system each year, and the timing and intensity of flu seasons can vary considerably from one year to the next.1 Last season’s peak influenza rate was as much as 90% higher than the prior two seasons.2 Tracking how early-season activity compares with prior years can offer an early read on the season ahead and inform the timing of vaccination campaigns and clinical preparedness.
Our communicable diseases data tracker follows complementary influenza measures updated every other week: the weekly rate of influenza encounters per 100,000 patients with an office, emergency department (ED), or inpatient visit, and the weekly share of influenza lab tests were positive. We studied influenza trends since 2022 to see how this season compares to other post-pandemic seasons.
September influenza rates are higher in 2026 than in any of the previous post-pandemic seasons. The week of September 13, 2026, the rate of encounters with an influenza diagnosis or positive test across all care settings reached 140.6 per 100,000 patients. In the two most recent seasons, the rate did not reach 140.6 per 100,000 until early November, roughly seven weeks later than this season. This year’s rate is about double the 2024 and 2025 levels for the same week (76.8 and 65.6 per 100,000). Those two seasons were unusually quiet and started later; in 2022 and 2023, mid-September activity was already elevated at about 94.6 and 101.5 per 100,000. The rate of influenza visits this year has increased earlier than any of the preceding four seasons, as shown in Figure 1. This rise was observed consistently across outpatient, ED, and inpatient care settings when evaluated independently.
Test positivity confirms that the early rise reflects an increase in influenza activity. Positivity reached 1.5% the week of September 13, 2026, the highest mid-September value in the post-pandemic era. Positivity rates for the same week in 2022 and 2023 were 0.8% and 0.9%, while the 2024 and 2025 seasons were nearly a third of this year’s positivity rate at 0.6% and 0.5%. Because positivity is a share of tests performed rather than a count of visits, its rise coinciding with the increased encounter rate indicates higher influenza prevalence rather than a change in how often people are tested.
Because influenza is arriving earlier this year than in recent seasons, timely vaccination is especially relevant this fall. The Advisory Committee on Immunization Practices (ACIP) recommends routine annual influenza vaccination for everyone aged six months and older who does not have a contraindication, ideally in September or October, with vaccination continuing throughout the season while influenza viruses are circulating.3
