Flu season is starting weeks earlier than usual in the Bay Area, and county health departments are urging residents not to wait until November to get vaccinated.

The signs are already here

Stanford's WastewaterSCAN project, which tracks viruses in sewage, shows the region has already crossed its seasonal threshold for flu, KQED reported. Last year that did not happen until November 2025. The project detected influenza in more than 90% of Bay Area samples in September, and concentrations rose almost 350% from August to September.

San Francisco's Department of Public Health announced on Oct. 1 that an adult resident had died after contracting the flu, the city's first flu-related death of the 2026-27 season, according to Bay City News. Last winter the city saw no flu deaths until January. As of mid-September, the California Department of Public Health counted 26 flu-related deaths statewide this season.

In Solano County, Acting Public Health Officer Dr. Cameron Kaiser told supervisors this week that flu cases are rising there too, the Vacaville Reporter reported. A Kaiser Permanente Vacaville infectious disease specialist said COVID-19 and RSV are also circulating.

When to get vaccinated

The CDC recommends a yearly flu shot for everyone 6 months and older, ideally by the end of October. Protection takes about two weeks to build. UCSF infectious disease expert Dr. Peter Chin-Hong told KQED he plans to get his shot before Halloween and that this year's vaccines are well matched to circulating strains. He added that an early start does not necessarily mean a worse season.

Santa Clara County issued an advisory Thursday saying early flu activity means now is the time to protect families against fall viruses.

Where to go

Flu shots are covered without extra cost by health insurance and are available at most pharmacies. It is safe to get the flu and updated COVID-19 vaccines at the same visit. In San Francisco, uninsured residents over 4 can get both free at the health department's immunization clinic at 27 Van Ness Ave. San Francisco officials also recommend RSV vaccination for adults over 75 and for babies, and suggest masks in crowded indoor spaces and staying home when sick.