Los Angeles County and state health officials have urged the public to take precautions against mosquito-borne illnesses following announcements of the county’s first death this year as a result of West Nile virus and elevated infections statewide.
The person who died was a San Fernando Valley resident hospitalized with neurological illness caused by severe West Nile virus, the LA County Department of Public Health reported Friday. Additional information about the deceased was not available.
West Nile virus infections documented in the county this year total 15. Long Beach and Pasadena have their own health departments and are not part of the county’s cumulative data.
People and animals acquire the virus through the bite of an infected mosquito. Most people who become infected show no symptoms, but about 1 in 5 develop a fever and other symptoms, according to health officials.
About 1 in 150 infected people escalate severe symptoms such as high fever, rashes, swollen lymph nodes, stiff neck and muscle weakness. Severe illnesses resulting from a West Nile virus infection can include meningitis, encephalitis and paralysis, according to health officials.
County and state health departments reported the number of infections is above the five-year average for this point in the annual season when mosquitoes are most active.
Half of LA County’s 2026 infections were in the San Fernando Valley, officials reported.
“We extend our heartfelt condolences to the family and friends grieving the loss of a loved one due to West Nile virus,” 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 suggested residents apply insect repellent, get rid of standing water where mosquitoes can breed and ensure windows and doors have tight-fitting screens with no holes or tears.
“Everyone can take simple steps to reduce their risk. … Small actions like these can make a big difference in preventing illness,” Davis said.
Also on Friday, the California Department of Public Health reported that West Nile virus activity statewide has reached the highest level in five years. As of Aug. 14, 30 human cases, including three deaths, have been reported in 13 counties.
In 2025 in LA County, two people died from infections, which totaled 22 with 18 requiring hospitalization.
“West Nile virus can be fatal, particularly for the elderly and immunocompromised,” CDPH Director and State Health Officer Dr. Erica Pan said in a statement. “August and September are peak periods of West Nile virus transmission in the state, so we urge everyone to take precautions to protect themselves against mosquito bites.”
Signs of West Nile virus activity are present in 32 California counties as a result of surveillance programs that monitor mosquito populations, dead birds, sentinel chickens and horses, according to state health officials.
Over 24% of dead birds identified through surveillance have tested positive for the virus, compared with the five-year average of 13%. Of every 1,000 mosquitoes, eight tested positive, above the five-year average of five virus-carrying mosquitoes per 1,000, according to state data.
Vector control districts in LA County this year have also reported an above-average number of positive mosquito pools and dead birds.
“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 in a statement.
Kluh said frequent virus detections continue despite efforts to suppress the number of mosquitoes. She urged residents to wear repellent when outdoors, especially around dawn and dusk.
People older than 50 and those with certain health conditions face a greater risk of serious illness.
There is no vaccine or specific treatment for West Nile virus.
Additional information is on the county’s website.
