U.S. Flu Season Starts Early with Mutated H1N1 Strain, CDC Reports
The 2026-2027 flu season in the United States has begun earlier than usual, with cases rising significantly since August, according to the U.S. Centers for Disease Control and Prevention (CDC). As of November 5, flu infections are increasing in 42 states, particularly in the West. The CDC's FluView surveillance report for the week ending October 31 indicated that early-season influenza activity is higher than typically observed. Currently, the H1N1 strain, a type of influenza A virus, is responsible for the majority of cases. This H1N1 strain has acquired a new mutation, G155E, which experts believe may affect its ability to evade pre-existing immunity. This is a shift from the previous winter, when influenza A H3N2 subclade K was the dominant strain. Experts like Andrew Pekosz, Ph.D., a virologist at Johns Hopkins Bloomberg School of Public Health, note that cases are still relatively low but are in the early phases of a surge. The percentage of positive flu tests was 9.1% during the week ending October 3...
