Orange County officials warn of "five-alarm year" for mosquitoes and West Nile virus

Orange County vector control officials are sounding the alarm on what they say is an unprecedented mosquito season. 

"This is a fire-alarm year for mosquitoes," said Brian Bannon, a spokesperson for the Orange County Mosquito and Vector Control District. "It's just off the charts."

The latest data from Orange County vector control shows that 718 mosquito nets have tested positive for West Nile virus, a drastic jump from the 70 recorded at the same time last year. So far in 2026, at least 18 people in Orange County have tested positive for the virus, another steep increase from the zero patients recorded in the first nine months of 2025. 

Bannon said that the mosquito population this year is unprecedented and that they're working with the Orange County Health Care Agency to spray and get rid of the nuisance. 

At midnight Wednesday, four vector control trucks were scheduled to hit the streets in Anaheim, Costa Mesa and Garden Grove to spray a pesticide aimed at killing adult mosquitoes with West Nile virus. Officials said the pesticide is an ultra-low-volume treatment that sprays approximately two tablespoons per acre.

"At the rate that we spray, it won't harm humans," Bannon said. "You can have your air conditioning on. It won't hurt the finish of your car. You can keep your windows open. It's just a very, very small amount and it's enough to knock down the mosquitoes"

Additionally, Bannon said that Vector Control biologists are growing mosquito fish to help curb the population. 

"These fish are used to manage populations of immature mosquitoes, larvae and pupae," said one OC Vector Control official. "The fish will actually eat the larvae when placed in a water source in the field."

In the meantime, officials urged people to dump standing water around their homes and to stay vigilant when outdoors, especially at dusk and dawn. They advise using bug spray and wearing long sleeves and pants to prevent bites.