West Nile virus in LA has reached its highest level in five years. As of Nov. 6, 2026, the California Department of Public Health counts 528 human cases statewide and 32 deaths, and Los Angeles County accounts for 13 of those deaths.
The state added 27 new cases in the latest weekly update. So even though cooler fall weather has slowed mosquitoes, residents still have reasons to take precautions.
West Nile virus in LA: the numbers so far
The state’s West Nile virus tracking page lists cases in 23 counties. Deaths cover nine jurisdictions. Los Angeles County has the most with 13, followed by Orange County with 7 and Butte County with 3.
CalMatters, in a story LAist republished on Nov. 9, reported that LA County also makes up more than half of the human cases. The same story said that at one point this summer, more than 70% of the mosquitoes trapped for testing carried the virus. That share has since fallen to about one-third.
The Greater Los Angeles County Vector Control District said in late September that activity remained high across its service area. The district covers much of the county, from the San Gabriel Valley to the Gateway Cities.
Why a wet winter matters
Mosquitoes breed in standing water. CalMatters reported that rain from a recent storm washed larvicide out of more than 3,000 miles of underground storm drains, which gave mosquitoes more places to breed.
Looking ahead, federal forecasters give a very strong El Niño a better than 90% chance this winter, according to the same report. Heavy rain would bring flooding, but standing water that lingers into spring could also help mosquito numbers grow as temperatures rise. For storm preparation, see our guide to free LA County sandbag events.
That said, the pattern may ease in some places. Birds that survive infection become immune, and outbreaks often run in three- to five-year cycles. CalMatters said LA and Orange counties could see a break next year, though other parts of California stay at risk.
What residents can do
State and local health agencies give the same basic advice:
- Empty standing water at least once a week, including pet dishes, plant saucers, toys and birdbaths.
- Use an EPA-registered repellent such as DEET, picaridin or oil of lemon eucalyptus.
- Wear long sleeves and pants outdoors between dusk and dawn.
- Report dead crows, ravens or scrub-jays at westnile.ca.gov.
The vector control district also inspects properties case by case. A single neglected green pool can produce up to 3 million mosquitoes in a month, the district says. Residents can file a service request through the district website or call (562) 944-9656.
Most infected people have no symptoms, but severe headache, a stiff neck, confusion or muscle weakness need prompt medical care. Risk is higher for people over 60. This is general information, not medical advice. For more public health coverage, visit our health and sports hub.