Public‑health officials across California report that this year’s influenza season began several months earlier than usual and in a region that typically sees the virus later. In Los Angeles County, flu activity started to climb in September, well before the normal early‑November onset, according to Dr. Dawn Terashita, associate director of the county’s Acute Communicable Disease Control Program.
Early onset and geographic shift
Dr. Terashita told The Times that the early rise is not entirely surprising because “flu tends to be very unpredictable” due to its constant mutation. What is unusual, she said, is that the season ignited in the Western United States rather than the South, where flu usually originates before moving northward, as explained by Dr. Elizabeth Hudson, regional chief of infectious diseases at Kaiser Permanente Southern California.
The county officially marked the start of its flu season on Sept. 28. While the premature start does not automatically signal a harsher season, the pattern of positive flu tests has been notable. The San Francisco Bay Area reports a high positivity rate, while Southern California and the Sacramento Valley show moderate levels. Hospital admission rates remain low statewide, and the California Department of Public Health’s dashboard lists 34 flu‑related deaths so far.
San Francisco confirmed its first flu death of the season last week. Los Angeles County, however, has not yet recorded a flu death this year, contrasting with the 2025‑26 season when the county logged 126 influenza deaths, a figure described by Dr. Terashita as relatively low.
Kaiser Permanente has observed a recent uptick in outpatient visits for flu‑like illness, though hospitalizations have not yet risen. Dr. Hudson cautioned that if the current trend continues, hospital admissions could increase in the coming weeks.
Vaccination push amid rising cases
Health officials are emphasizing vaccination as the primary defense. Dr. Peter Chin‑Hong, an infectious‑disease specialist at UC San Francisco, advises residents to receive their flu shot ideally before mid‑October. He noted that the standard injectable vaccine is appropriate for most people, while a nasal spray option is available for those who prefer to avoid needles. For adults 65 and older, higher‑dose shots containing four times the antigen are approved.
The circulating strain this season is identified as H3N2 subclade K, which closely resembles last year’s virus and is included in the current vaccine formulation. “The ball is in our court because vaccination behavior drives how we tackle the flu,” Dr. Chin‑Hong said. “This year we have less excuse because the flu vaccine is well‑matched in general to what has been circulating so far.”
Historical context underscores the importance of immunization. The most severe recent flu season in Los Angeles County was the 2009 H1N1 pandemic, which caused a sharp rise in hospitalizations and deaths worldwide. Flu activity had nearly vanished during the COVID‑19 pandemic, but as masking and social‑distancing measures relaxed, cases began to climb again in 2024 and 2025.
Dr. Terashita summed up the current outlook: “We’re just watching and waiting right now to see how severe the flu season will be, but it is a good reminder to everyone that it’s a very good thing you can do to protect yourself, which is get the vaccine.”
Rong‑Gong Lin contributed to the reporting.
Mitchell Landsberg is a Senior Technology Correspondent at News Raise. He covers consumer electronics, artificial intelligence, software developments, and digital privacy trends.
