Flu season has arrived in the United States weeks ahead of its typical schedule, with early activity concentrated in Western states. Infectious disease experts report a rise in cases driven by a potentially immune-evasive H1N1 variant and are urging people to get vaccinated now to ensure protection throughout the season.
An Unusually Early Start in the West
While autumn typically marks the beginning of respiratory virus season, data from the week of September 13, 2026, shows that influenza encounter rates reached 140.6 per 100,000 patients, a level not seen until early November in the two previous years, according to data from Epic Research. This acceleration has been observed consistently across outpatient, emergency department, and inpatient settings. In 2022 and 2023, mid-September activity was recorded at 94.6 and 101.5 per 100,000, respectively, making the current year’s increase the earliest rise in the preceding four seasons.
The geographic pattern of this season is also diverging from historical norms. Caitlin Rivers, an epidemiologist at the Johns Hopkins Bloomberg School of Public Health, noted that flu typically originates in the South before migrating north and west. Because it is appearing in states like Washington, Alaska, Hawaii, and California first, Rivers describes these as two uncommon developments.
The Role of H1N1 Variants
Researchers investigating the early surge point to a potential shift in the virus’s makeup. This mutation appears to allow the virus to better evade antibodies. Amesh Adalja, M.D., a senior scholar at the Johns Hopkins Center for Health Security, notes that this H1N1 strain is more common this time of year and is currently infecting more susceptible individuals, leading to faster spread.
While some have suggested that low vaccination rates could be a factor, experts like Dr. Thomas Russo, a professor and chief of infectious disease at the University at Buffalo in New York, argue that it is too early in the year to attribute the trend to public behavior, as many people have not yet sought their annual shots. That’s the normal baseline, not a new factor,
Dr. Adalja agrees.
Vaccination Guidance for the 2026-27 Season
Despite the early start, public health officials emphasize that the season’s onset does not necessarily predict its final severity. Nevertheless, clinicians are encouraging earlier vaccination to allow the body time to develop an immune response. Dr. Kaylan Christianer, a primary care doctor and assistant professor of medicine at Columbia University Vagelos College of Physicians and Surgeons, added that the vaccine takes roughly two weeks to become fully effective.
Annette Regan, an Adjunct Associate Professor of Epidemiology at the University of California, Los Angeles, notes that there are several options available, including the new mRNA influenza vaccine approved by the FDA in August 2026.
- Standard-dose inactivated vaccines: Available for anyone 6 months and older; administered as injections.
- High-dose and adjuvanted vaccines: Recommended for adults aged 65 and older to provide a stronger immune response due to higher risk of severe illness.
- Recombinant flu vaccines: Egg-free options for individuals aged 9 and older.
- mRNA vaccine (mFLUSIVA): A new option approved by the FDA for adults aged 50 and older.
- Nasal spray: Available for individuals aged 2 through 49 who are not pregnant and do not have certain medical conditions.
For those concerned about the timing, health authorities advise that getting a shot before flu activity becomes widespread provides the best chance of protection. And this might be a year that people might want to get a vaccine early.
The CDC estimates that since 2010, the flu has resulted in between 120,000 and 710,000 hospitalizations annually in the U.S., with deaths ranging from 6,300 to 52,000. Dr. Dawn Terashita of Los Angeles County noted that the county is currently in a “wait and see” period regarding the season’s severity. As of early October, California reported 34 flu-related deaths, and San Francisco confirmed its first death of the season. Dr. Terashita reminded residents that while the 2025-26 season saw 126 flu deaths in the county—a relatively low total—the 2009 pandemic remains the most severe in recent memory.
Patients with underlying conditions, such as heart, kidney, or liver disease, are encouraged to seek prompt testing and care to avoid complications. Readers should consult with a qualified healthcare provider or pharmacist to determine the most appropriate vaccination strategy for their specific health needs.
