Public health officials in Placer County have confirmed the first mosquito in the area to test positive for West Nile virus (WNV) in 2025. The mosquito was found during routine trapping in an agricultural zone near Phillip Road in unincorporated Placer County.

With continued warm weather, vector control experts anticipate that more WNV activity will follow this early detection. Officials emphasize the urgency of mosquito prevention at home: remove standing water from flowerpots, gutters, and other containers, and apply EPA-registered repellents when spending time outdoors.

While the virus is common in California, human infection remains rare. According to Placer County Mosquito and Vector Control, only about 1% of those infected develop symptoms. Nonetheless, symptoms—such as fever, headache, body aches, and fatigue—can become serious in rare cases.

Although no human cases of WNV have been reported in California as of mid-June 2025, this detection signals the start of the season. Local agencies continue monitoring and encourage residents to stay informed and report mosquito problems.