Stanislaus County reports first West Nile virus death of 2026

A Stanislaus County resident has died from a severe form of West Nile virus, marking the county's first West Nile-associated death of 2026.

Health officials said the person developed neuroinvasive West Nile virus, a rare form of the disease that can affect the brain and nervous system. No other information was released, other than that the person was under 50.

"While the risk of severe illness increases with age and certain health conditions, West Nile virus can cause serious illness in people of any age," county Public Health Officer Dr. Thea Papasozomenos said.

Stanislaus County had recorded 11 human West Nile cases this year as of Sept. 22, including the person who died.

Officials say this has been an especially active West Nile season across California.

The state's latest surveillance update, covering cases reported through Sept. 18, showed 147 human infections across 21 counties and 10 deaths. Those numbers do not yet include Stanislaus County's newly announced death and may lag newer local case counts.

California health officials said in August that West Nile activity had reached its highest level in five years. Human cases were already running above the recent five-year average for that point in the season.

The virus is also showing up widely in mosquitoes and birds. As of Sept. 18, more than 3,500 mosquito samples and 600 dead birds had tested positive statewide.

West Nile spreads primarily through the bite of an infected mosquito. Most people who get it never develop symptoms, while others may experience fever, headaches and body aches. In rare cases, the virus can cause serious brain or nervous system illnesses such as encephalitis or meningitis.

There is no vaccine or specific treatment for West Nile in humans, making mosquito-bite prevention the main way people can protect themselves.