Orange County reports record levels of West Nile-positive mosquitoes

The Orange County Mosquito Vector and Control District said the 2024 season is on pace to produce the highest count of West Nile virus-positive mosquito pools in the district’s history. As of July 24, officials had recorded 102 positive pools, compared with 186 in the entire 2025 season, and the virus has been detected in 16 cities, with the greatest concentrations in Anaheim, Buena Park and Fullerton.

"We are well on our way to having the most heavy amount of West Nile virus activity in the history of Orange County and the Mosquito Vector and Control District," spokesperson Brian Brannon said.

The district, which first identified West Nile-positive samples on June 2 in Newport Beach, attributes the surge to an unusually warm year that accelerates mosquito breeding. To curb the spread, crews in specially equipped Jeeps treat standing water along curbs with mineral oil to block mosquito larvae from breathing. Since May, the agency has also released up to 100,000 sterilized male mosquitoes in Mission Viejo to reduce the breeding population.

Public health officials note that most infections are asymptomatic, but about one in five people develop flu-like symptoms, and severe cases can cause brain inflammation, hospitalization or death. The Centers for Disease Control and Prevention estimates roughly 2,000 U.S. cases are diagnosed each year, with a 10% mortality rate among severe infections.

Residents are urged to eliminate standing water around homes, use EPA-registered repellents, wear long sleeves and light-colored clothing at dusk and dawn, and keep windows screened. The district offers free mosquito-control services on a first-come, first-served basis and asks the public to report dead birds and high mosquito activity.

"If people are seeing mosquitoes or home issues and they want us to come out, better call now, because it looks like we’re going to be pretty busy throughout the summer," Brannon added.