Riverside County Vector Control Program has confirmed its first two detections of West Nile Virus (WNV) in the unincorporated areas of Riverside County for the 2026 mosquito season. These are the first locally detected positives of WNV for the jurisdiction covered by Riverside County Department of Environmental Health’s Vector Control Program.
The first positive mosquito pool was identified during routine surveillance in Nuevo. The second detection was confirmed through laboratory testing of a dead bird found near Spencer’s Park in the unincorporated area of Murrieta.
“West Nile Virus has been detected in our community,” Riverside Third District Supervisor Chuck Washington said. “While the county is increasing surveillance and taking action to monitor the situation, there are simple steps we can all take to help protect our families and neighbors. Use repellent, dump standing water, and stay alert during dawn and dusk. Together, these small steps can make a big difference in keeping our community mosquito-safe.”
In response to the positive mosquito pool in Nuevo, the Riverside County Vector Control Program will conduct an ultra‑low‑volume (ULV) ground application using truck‑mounted sprayers to reduce adult mosquito populations in the affected area on Tuesday, August 25, from 4:30 a.m. to 7 a.m. Aqua Reslin, an EPA‑approved mosquito control product, will be applied by trained and certified technicians.
Although Aqua Reslin poses very low to no risk to people and animals, to avoid exposure, residents and pets should remain indoors and keep windows closed for 15 minutes after the application. The ULV treatment uses 0.5 ounces per acre, a rate designed to be safe for humans, pets, and crops.
Notification signs will be posted along treatment routes beginning Friday, August 21.
Treatment will occur in three defined zones: Mystic Field, Wet Nuevo, and East Nuevo.
Following the positive WNV bird detection, Vector Control staff are increasing surveillance efforts in the Murrieta area, identifying potential breeding sites and conducting larval control where needed. At this time, no mosquito samples collected within the district’s service area where this bird was collected have tested positive for WNV.
Residents are encouraged to take proactive steps to protect themselves and reduce mosquito breeding around their homes.
“A little repellent goes a long way, Riverside County Fifth District Supervisor Yxstian Gutierrez said. “Choosing products with DEET, picaridin, oil of lemon eucalyptus, or IR3535 helps keep mosquitoes away and protects your family. Just remember to use age‑appropriate options for young children. Stay safe, stay bite‑free, Riverside County.”
Residents may call the Riverside County Vector Control office at 951‑766‑9454 to report mosquito problems, ask questions, or request mosquito‑eating fish.
More information, visit https://rivcoeh.org/vector-control.
