Tuesday, 28 July 2026, 10:02
The Los Angeles County Department of Public Health announced Monday the county's first human case of West Nile virus in 2026. The infected individual, a resident of the Antelope Valley, was hospitalized after developing West Nile virus encephalitis—a rare but serious neurological condition that occurs in less than 1% of infected patients, according to the CDC. Symptoms began in late June.
“The first human cases of West Nile virus are an important reminder that we all need to take steps to prevent mosquito bites and mosquito breeding,” said Muntu Davis, MD, MPH, Los Angeles County Health Officer. “Mosquitos thrive in hot weather, increasing the risk of bites and mosquito-borne diseases. People should follow these simple steps to reduce their risk of exposure: 1) Use insect repellent on you and your family; 2) Remove items that hold standing water around your home where mosquitoes can lay eggs and breed and 3) Use, install, or repair window and door screens to prevent mosquitoes from entering your home.”
Officials also encouraged residents to report neglected swimming pools that could serve as mosquito breeding grounds and to notify authorities when dead birds are found, since increases in infected birds often precede human cases of the virus.
West Nile virus encephalitis can cause fever, altered mental status, and movement disorders, the CDC reports. The patient's hospitalization underscores the potential severity of the disease, which can also lead to meningitis, paralysis, or death in extreme cases. Those over 50 and individuals with preexisting conditions face higher risks. Recovery from severe illness can take weeks or months and approximately one in every 10 patients with severe neurological illness die from complications. In more severe cases, symptoms include high fever, headache, neck stiffness, vision loss, paralysis and coma. These more severe symptoms may last several weeks and lead to permanent damage to the brain and nervous system.
Federal and local officials report West Nile virus activity is well above average for this time of year. By the end of June, at least 48 human cases were recorded nationwide, 38 of which were severe neuroinvasive disease. In California, three cases have been confirmed: this LA County case, one in Sacramento County, and one in Long Beach. LA County averages 41 human cases per year over the last five years, though many infections go undiagnosed. This does not include cases in Long Beach and Pasadena as cases identified in those cities are reported by their local health departments. The Los Angeles Public Health Department noted that the total number of people infected with West Nile virus each year in L.A. County is much higher as most infected people do not experience any illness or only mild illness.
The Antelope Valley Mosquito and Vector Control District has been monitoring the virus for decades. “Detecting West Nile virus in our district is a reminder that this virus has been present in California, and right here in our community, for over 20 years,” said Brenna Bates-Grubb, community outreach specialist. The district warns that mosquito-borne diseases are a recurring seasonal threat, especially during hot weather when mosquitoes thrive. “We urge everyone to take simple steps to protect themselves and their families: use EPA-approved mosquito repellent, keep swimming pools clean and maintained, drain any standing water around your home, and check for sources like buckets, plant saucers or clogged gutters that can fill with rainwater. It only takes a small amount of water for mosquitoes to breed.” The virus-carrying mosquitoes and the infections that ensue are “part of our local environment and continue to reappear year after year,” Bates-Grubb said in a statement.
In 2025, the Greater Los Angeles County Vector Control District detected West Nile virus in mosquito samples from numerous communities, including Arleta, Artesia, Bellflower, Burbank, Canoga Park, Carson, Cerritos, Cudahy, Downey, Encino, Florence-Firestone, Gardena, Glassell Park, Granada Hills, Hacienda Heights, Hawaiian Gardens, Hollywood Hills, Lake Balboa, Lake View Terrace, Lakewood, Long Beach, Los Angeles (South Park and South Central), Mission Hills, Montebello, North Hills, North Hollywood, Northridge, Norwalk, Pacoima, Panorama City, Pico Rivera, Porter Ranch, Reseda, Santa Fe Springs, Sherman Oaks, Signal Hill, South El Monte, Studio City, Sun Valley, Tarzana, Toluca Lake, Valley Glen, Valley Village, Van Nuys, West Hills, Wilmington, and Winnetka. A total of 180 positive mosquito samples were reported. Additionally, four dead birds tested positive for the virus in Glendale, North Hollywood, Norwalk, and Sherman Oaks. The district uses factors such as higher-than-average temperatures, mosquito population monitoring, mosquito testing, dead bird reports, and sentinel chickens to assess health risk and guide response efforts.
In the Inland Empire, mosquitoes collected in the city of San Bernardino have tested positive for West Nile virus, county officials announced earlier this month. This is the first collection of mosquitoes that have tested positive in 2026 within the area served by the county’s Environmental Health Services Mosquito and Vector Control Program. The program is taking steps to eliminate mosquito breeding hazards, according to the county. “West Nile virus can cause serious illness in humans, so I encourage residents to take steps to protect themselves from mosquito bites,” San Bernardino County Health Officer Dr. Sharon Wang said in a statement. “Community awareness and consistent prevention efforts play an important role in reducing mosquito populations and lowering the risk of West Nile virus.” In Riverside County, mosquito samples in the communities of North Shore and Mecca tested positive for the virus, the Coachella Valley Mosquito and Vector Control District announced Friday. The North Shore sample was collected in the area of Avenue 72 and Cleveland Street, while the other samples were collected in the areas of Avenue 70 and Johnson Street and Avenue 71 and Grant Street in Mecca. The district performed periodic control treatments using truck-mounted equipment throughout June in Desert Hot Springs, Palm Springs and North Shore. The next so-called Wide Area Larvicide treatments are set for 1 a.m. to 7 a.m. on Sept. 12, 19 and 26 and on Oct. 3. According to the district, the treatments target mosquitoes in standing water to reduce their population. The products are EPA-registered and considered safe for people, pets, wildlife and honeybees. Maps of the spraying operations are available at cvmosquito.org/wide-area-larvicide-treatments-summer-2026.
West Nile virus first appeared in California in 2003 and has since become the most common and serious mosquito-borne disease in the state. It is transmitted to humans through the bite of an infected Culex mosquito, which acquires the virus by feeding on infected birds. There is no vaccine or specific antiviral treatment; prevention relies entirely on mosquito control and bite avoidance.
Health officials urge everyone to take simple precautions to reduce risk. Use EPA-approved repellents containing DEET, Picaridin, IR3535, or oil of lemon eucalyptus. Wear long sleeves and pants at dawn and dusk, when mosquitoes are most active. Eliminate standing water around homes—in buckets, plant saucers, birdbaths, and clogged gutters—and report neglected swimming pools to vector control. Stock garden ponds with mosquito-eating fish like Gambusia. Report dead birds to local authorities, as they help track virus spread. Additionally, use, install or repair window and door screens to prevent mosquitoes from entering your home, and clean and chlorinate swimming pools; drain any water collecting on pool covers. A majority of people who become infected with the virus are asymptomatic. Others will experience mild symptoms such as fever, body aches and nausea.
