Los Angeles County Reports First West Nile Virus Death of 2026 as Cases Spike After Record Warm Winter

LOS ANGELES — Los Angeles County health officials confirmed the first West Nile virus death of 2026 this week, a San Fernando Valley resident who died after hospitalization with a severe neurological illness caused by the mosquito-borne virus, as cases in the county and across California climbed above recent averages following an unusually warm winter.

The Los Angeles County Department of Public Health announced the fatality on Thursday, noting that the individual developed neurological complications from a severe West Nile virus infection. No further details about the resident's age, gender or specific medical history were released. The department reported 15 documented West Nile virus infections in the county so far this year, excluding Long Beach and Pasadena, which maintain separate health departments. Of those, 14 were symptomatic, with the most recent onset dated Aug. 6. Roughly half of the infected residents lived in the San Fernando Valley.

County figures for human infections this season exceed the five-year average for the same period. Mosquito pools and dead birds have tested positive across multiple areas of Los Angeles County, signaling elevated virus activity that began earlier than typical.

"We extend our heartfelt condolences to the family and friends grieving the loss of a loved one due to West Nile virus," Los Angeles County Health Officer Dr. Muntu Davis said in a statement. "This tragic loss is a reminder of the serious threat posed by mosquito-borne diseases, including West Nile virus and dengue."

Davis urged residents to take protective steps, including using insect repellent containing DEET, eliminating sources of standing water where mosquitoes breed, and ensuring windows and doors have tight-fitting screens. "Small actions like these can make a big difference in preventing illness," he said.

The county's announcement coincided with a California Department of Public Health report that statewide West Nile virus activity has reached its highest level in five years. As of Aug. 14, the state had recorded 30 symptomatic human cases across 13 counties, including three deaths. Positive mosquito pools and dead birds were also reported at levels higher than the five-year average.

Vector control officials attributed the early and widespread activity in part to weather patterns. "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," said Susanne Kluh, general manager of the Greater Los Angeles County Vector Control District.

Kluh noted that while overall mosquito abundance has been somewhat suppressed in some areas, virus detections remain frequent. Officials continue to urge residents to wear repellent when outdoors, particularly at dawn and dusk when the mosquitoes that transmit West Nile virus are most active.

West Nile virus is the most common mosquito-borne disease in Los Angeles County and has been present in the region since it first emerged in 2004. The virus circulates in birds and is transmitted to humans primarily through the bite of infected Culex mosquitoes. Most people infected with West Nile virus experience no symptoms or only mild ones, such as fever, headache, body aches, joint pain, vomiting, diarrhea or rash. A smaller percentage develop severe neuroinvasive disease, which can include encephalitis, meningitis or acute flaccid paralysis. Older adults and people with weakened immune systems face higher risks of serious illness and death.

In 2025, Los Angeles County recorded 22 infections and two deaths. Earlier years showed greater variation, with higher case counts during peak seasons in the mid-2010s. Statewide surveillance this year has shown elevated positivity rates among tested dead birds—around 24 percent compared with a five-year average of 13 percent in some reports—serving as an early warning indicator because birds amplify the virus before it spreads to mosquitoes and people.

The San Fernando Valley has long registered some of the highest rates of West Nile virus activity in the county. Local vector control agencies have detected positive mosquito samples and dead birds in numerous communities throughout the greater Los Angeles area, including parts of the Antelope Valley, where the county's first human case of the 2026 season was identified in July. That earlier patient, an Antelope Valley resident, was hospitalized with West Nile encephalitis after symptoms began in late June.

Public health and vector control districts emphasize simple prevention measures that residents can take immediately. Removing standing water from flower pots, birdbaths, gutters, unused swimming pools and other containers reduces breeding sites. Maintaining swimming pools and reporting neglected ones to local agencies helps limit mosquito populations. Using EPA-registered insect repellents, wearing long sleeves and pants when outdoors during peak mosquito hours, and installing or repairing screens provide additional layers of protection.

Officials also encourage the public to report dead birds, which can be tested for the virus and help map areas of higher risk. Dead bird reports and mosquito pool testing form the backbone of surveillance systems that guide targeted control efforts, such as larviciding and adult mosquito treatments in high-activity zones.

California's overall West Nile virus season typically peaks in August and September. With activity already elevated and transmission continuing, health authorities expect additional cases in the coming weeks. The Centers for Disease Control and Prevention tracks West Nile virus nationally and notes that the disease causes more than 100 deaths in the contiguous United States in an average year, with severe cases carrying a fatality rate of roughly 10 percent among those who develop neuroinvasive illness.

In Los Angeles County, the combination of early virus amplification, higher-than-average human infections and the first confirmed death of the season has prompted renewed public messaging. County and state officials continue to monitor mosquito and bird surveillance data closely while coordinating with local vector control districts to reduce mosquito populations in affected neighborhoods.

Residents who develop symptoms consistent with West Nile virus infection, particularly high fever, severe headache, neck stiffness, confusion, muscle weakness or paralysis, are advised to seek medical attention promptly and inform their health care providers of possible mosquito exposure. There is no specific antiviral treatment or vaccine available for West Nile virus in humans; care focuses on supportive measures for severe cases.

As the peak transmission period continues, public health leaders stress that individual actions remain the most effective tool for reducing risk. By eliminating standing water, using repellent consistently and taking basic outdoor precautions, residents can lower their chances of infection even in a season marked by elevated virus activity.

The Los Angeles County Department of Public Health will continue updating its weekly arboviral disease reports throughout the season. The most recent report, dated Aug. 21, confirmed the 15 infections and single death to date and underscored that the number of infections exceeds historical averages for this point in the year. Statewide figures are expected to rise as testing and reporting continue in the weeks ahead.

Health officials reiterated their condolences to the family of the San Fernando Valley resident while calling on the broader community to remain vigilant. With mosquitoes still active and virus detections ongoing across many parts of the county, the coming weeks will determine the full scale of the 2026 West Nile virus season in Los Angeles County and California.