Los Angeles County health officials urged residents Tuesday to take precautions against mosquitoes after reporting the county’s first human case of West Nile virus this year in an Antelope Valley resident.
The resident was hospitalized after developing West Nile virus encephalitis following the onset of symptoms in late June, according to the LA County Department of Public Health.
“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,” county Health Officer Dr. Muntu Davis said in a statement. “Mosquitoes thrive in hot weather, increasing the risk of bites and mosquito-borne diseases.”
Davis said residents should apply insect repellent, get rid of standing water around homes where mosquitoes can breed and make sure window and door screens are installed and maintained properly.
Officials also said residents should report neglected swimming pools that are potential mosquito breeding grounds and to notify authorities when dead birds are found. Increases in infected birds often precede human cases of West Nile virus.
“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,” Brenna Bates-Grubb of the Antelope Valley Mosquito and Vector Control District said. “It’s part of our local environment and continues to reappear year after year.”
Human cases of West Nile virus each year in Los Angeles County average 41 over the last five years, excluding cases reported separately by the Pasadena and Long Beach health departments, officials said.
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.
West Nile virus spreads to humans when a female mosquito becomes a carrier by biting an infected bird. If a person becomes infected, few experience mild or no symptoms, while serious illness may develop in others. People over 50 years old are at greater risk for severe complications, vector officials said.
Vector control districts urged residents to take the precautions as mosquito activity increases during the year’s warmer months:
- Dump and drain standing water around homes, including flowerpots, buckets and tires.
- Wear insect repellent containing EPA-registered active ingredients when outdoors.
- Wear long sleeves and pants during dawn and dusk when mosquitoes are most active.
- Report neglected pools or significant mosquito activity to the district.
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 that are considered safe for people, pets, wildlife and honeybees.
Maps of the spraying operations are on the internet: cvmosquito.org/wide-area-larvicide-treatments-summer-2026.
No vaccine or specific treatment exists for West Nile virus.
A state website has more information on the virus, westnile.ca.gov.
