LA County health officials reported the first local death due to West Nile virus for the 2025 mosquito season. The person, a resident of San Fernando Valley, was hospitalized and died from neurological illness caused by severe West Nile virus.
A total of 14 West Nile virus infections have been documented in Los Angeles County so far this year (excluding Long Beach and Pasadena as cases identified in those cities are reported by their local health departments). Half of infected people live in the San Fernando Valley region (50%).
Peak mosquito season lasts from June to November in LA County.
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West Nile virus is a disease caused by the bites of infected mosquitoes. The virus survives in nature in several types of birds and is transmitted by the bites of mosquitoes that feed on infected birds. West Nile virus spreads during warm weather months when mosquitoes are most active. While not all mosquitoes carry this virus, the type of mosquito that spreads this virus is found throughout Los Angeles County. While everyone is at risk for West Nile virus, people over 50 and those with health problems are at greater risk of serious illness, which can include meningitis (brain infection), encephalitis (swelling of the brain) and limb paralysis. There is no specific treatment for West Nile virus disease and no vaccine to prevent infection.
Most people who get West Nile virus don’t have any symptoms. About 1 in 5 people who are infected develop a fever with other symptoms such as: headache, body aches, joint pains, vomiting, diarrhea and a rash.
About 1 in 150 people will have severe symptoms that may include high fever, stiff neck, muscle weakness, and sometimes rash. Symptoms usually appear 3 to 14 days after being infected. If symptoms are severe, residents are encouraged to call their doctor right away.