A San Fernando Valley resident has died from West Nile virus, the first fatality from the mosquito-borne illness in Los Angeles County this year.
The LA County Department of Public Health confirmed the death Thursday, Aug. 20. The resident had been hospitalized with a neurological illness caused by a severe West Nile infection, according to NBC Los Angeles. No other personal details were released.
The death comes as California's West Nile activity has reached its highest level in five years. Statewide, 30 human cases and three deaths had been recorded as of Aug. 14, nearly triple the five-year average for this point in the season, according to the California Department of Public Health.
LA County alone has logged 15 infections so far in 2026. Half of those patients live in the San Fernando Valley.
What's driving the surge
An abnormally warm winter and a record-breaking March heat wave fueled a surge in Culex mosquitoes, the species that carries West Nile in California, the Los Angeles Times reported. Virus detection in LA County started almost two months earlier than usual.
"After experiencing the warmest winter on record, West Nile virus amplification and consequently detection in Los Angeles County started almost two months early this year, leading to widespread activity countywide," Susanne Kluh, general manager of the Greater Los Angeles County Vector Control District, said Thursday, Aug. 20.
LA County's positive mosquito samples are 10 times higher this year than last, according to Dr. Matt Willis, an epidemiologist and former Marin County public health officer. Statewide, 373 dead birds have tested positive for the virus, compared to 76 at the same point in 2025.
Who's at risk
Most people bitten by an infected mosquito never develop symptoms. About one in five get fever, body aches or nausea. But roughly one in 150 develop severe neurological illness, including meningitis or encephalitis. People older than 50 and those with conditions like diabetes, high blood pressure or weakened immune systems face the greatest danger.
This year, about 93% of California's reported cases have involved neuroinvasive symptoms, according to SFGate. One in 10 patients with neuroinvasive West Nile disease will die.
There is no vaccine and no specific treatment.
How to protect yourself
LA County Public Health recommends residents:
- Use repellents containing DEET, picaridin, IR3535, 2-undecanone or oil of lemon eucalyptus
- Wear long sleeves and pants outdoors, especially from dusk to dawn when Culex mosquitoes are most active
- Check that window and door screens fit tightly with no gaps
- Dump any standing water around the home, including in plant saucers, buckets and pet bowls
Symptoms typically appear 3 to 14 days after a bite. August and September are peak transmission months in California, according to CDPH Director Dr. Erica Pan.
Residents can report dead birds, a key surveillance tool, at westnile.ca.gov or by calling 1-877-WNV-BIRD (1-877-968-2473).
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