Flu activity spikes in September, prompting early vaccination push in California

Flu activity in Los Angeles County began increasing in late September, several months ahead of the typical early-November onset, according to Dr. Dawn Terashita of the county's Department of Public Health. The early surge, which also appears in parts of the Western United States, has led officials to advise residents to obtain flu shots as soon as possible.

Terashita noted that while flu viruses are inherently unpredictable, the current rise does not necessarily signal a more severe season. Positive test rates have been high in the San Francisco Bay Area and moderate in Southern California and the Sacramento Valley, but hospital admissions remain low statewide. So far, California has recorded 34 flu-related deaths, with San Francisco reporting its first death of the season last week; Los Angeles County has not yet logged any influenza deaths.

Public health experts emphasize vaccination as the primary preventive measure. > "The ball is in our court because vaccination behavior drives how we tackle the flu," said Dr. Peter Chin-Hong, an infectious-disease specialist at UC San Francisco. He recommended that most people receive the standard flu shot before mid-October, noting that higher-dose formulations are available for adults 65 and older and a nasal spray option exists for those who prefer not to use a needle. The vaccine this year targets the H3N2 subclade K strain, which closely matches the virus currently circulating.

Terashita recalled that the 2009 H1N1 pandemic was the county's most severe recent flu season and that flu cases had largely vanished during the COVID-19 pandemic. With easing of masking and distancing measures, case numbers have risen again in 2024 and 2025. She said officials are monitoring the situation and reiterated the importance of vaccination to protect the community.