First mosquitoes infected with West Nile virus found in O.C.

Orange County vector control officials on Tuesday urged residents to take precautions against insect bites after mosquitoes found in samples collected in Newport Beach tested positive for West Nile virus.

Taken on May 28 from an area bordered by Campus Drive, Jamboree Road, State Route 73 and John Wayne Airport, the samples are the first evidence of the virus in the county this year, according to a release from the Orange County Mosquito and Vector Control District (OCMVCD).

Amber Semrow, the agency’s director of scientific and technical services, said the timing of the discovery may portend a particularly pernicious virus season.

“This is an early positive detection of West Nile virus activity in Orange County and it is in line with activity seen in neighboring counties right now confirming that conditions across the region are favorable for sustained virus activity,” Semrow said in the statement.

Last month, Los Angeles County officials found positive samples in Long Beach, Pico Rivera, Cerritos, Sunland and Hawaiian Gardens. In 2025, Orange County’s first infected mosquito was reported in late July.

West Nile virus is primarily transmitted to humans through the bite of infected mosquitoes, which get the virus when feeding on infected birds. So far, in Orange County there have been no reported human infections, vector control officials reported Tuesday.

Staff will continue to conduct surveillance, inspections and control measures to limit mosquito breeding. The agency encourages residents to drain containers holding water at least weekly, clean and scrub bird baths and pet water bowls and close all unscreened doors or windows.

People should protect themselves from bites by wearing insect repellent containing DEET, oil of lemon eucalyptus, Picaridin or IR3535 and wearing light-colored, loose-fitting, long-sleeved shirts and pants while outside at dawn and dusk.

“We all need to work together to fight mosquitoes,” OCMVCD spokesperson Brian Brannon said Tuesday. “Dumping and draining standing water is the most effective and environmentally friendly way to rid mosquitoes from our communities.”

For more information about prevention, visit ocvector.org.