Orange County Mosquitoes Reach Alarming Levels

Orange County vector control officials are raising concerns about an "unprecedented" mosquito season, describing the situation as "off the charts." Data from the Orange County Mosquito and Vector Control District reveals a dramatic increase in West Nile virus.

As of September 16, 2026, 718 mosquito traps have tested positive for West Nile virus, a stark contrast to the 70 positive traps recorded at the same point last year. The number of human cases has also surged, with 18 Orange County residents testing positive for the virus this year, compared to zero recorded during the first nine months of 2025.

To combat the escalating mosquito population, vector control is implementing a multi-pronged strategy. This includes spraying pesticides in affected areas like Anaheim, Costa Mesa, and Garden Grove. The pesticide used is an ultra-low-volume treatment, applied at a rate that officials state will not harm humans, pets, or vehicles.

Additionally, biologists are cultivating mosquito fish, which are effective in controlling populations of immature mosquitoes, such as larvae and pupae, by consuming them in water sources. Residents are advised to eliminate standing water around their homes and take protective measures when outdoors, especially during dusk and dawn, including using bug spray and wearing protective clothing.