Flu is circulating earlier than usual in the Bay Area, and state surveillance data show the region with the highest share of positive flu tests in California.
On Thursday, San Francisco's Department of Public Health reported that an adult in the city had died after contracting influenza. It was the first flu-related death there in the 2026-27 season, and the department did not release more details about the person.
"This sad news reminds us that respiratory viruses such as flu and COVID should be taken very seriously, especially for people who are at higher risk of getting sick," San Francisco Health Officer Dr. Susan Philip said.
What the state numbers show
The California Department of Public Health's respiratory virus dashboard has laboratory data through the week ending Sept. 12. In that week, 5.4% of Bay Area flu tests were positive. Statewide the figure was 3.9%, and every other region that reported was below 4%. The Bay Area share has risen every week since mid-August, when it stood at 3.4%.
Hospital admissions have stayed low so far. The state rated the Bay Area's flu admission rate that week, about 0.5 per 100,000 residents, as "very low."
Wastewater in Alameda County
Wastewater testing can give an earlier signal of spread. Federal data for the week ending Sept. 26 put influenza A levels at Alameda County treatment plants between "very low" and "moderate." The largest monitored plant, which serves about 740,000 people in Alameda and Contra Costa counties, moved up to moderate that week.
