Riverside County confirms season's first West Nile virus detections in Nuevo and near Murrieta
The county's Vector Control Program reported a positive mosquito pool in Nuevo and a positive dead bird near Spencer's Park, and scheduled truck-mounted spraying in three Nuevo zones for Aug. 25.
Riverside County's Vector Control Program confirmed its first two West Nile virus detections of the 2026 mosquito season in unincorporated areas, the county said in a news release dated Aug. 20.
The first was a positive mosquito pool found in Nuevo during routine surveillance, according to the release. The second was a dead bird, collected near Spencer's Park in an unincorporated area by Murrieta, that tested positive in a laboratory.
The county said no local positives had been detected earlier this season in the territory its Department of Environmental Health covers for vector control.
Spraying scheduled in Nuevo
In response to the Nuevo mosquito pool, the county said the program would carry out an ultra-low-volume ground application using sprayers mounted on trucks, aimed at cutting the number of adult mosquitoes.
The treatment was scheduled for Tuesday, Aug. 25, from 4:30 a.m. to 7 a.m., the release said. Notification signs were to go up along the treatment routes starting Friday, Aug. 21.
The county listed three treatment zones in Nuevo:
- An area bounded by Reservoir Avenue on the north, Orange Street on the east, Lakeview Avenue on the south and Magnolia Avenue on the west.
- An area bounded by 9th Street, Yucca Avenue, 10th Street and Reservoir Avenue.
- An area bounded by Reservoir Avenue, 5th Street, Lakeview Avenue E and 6th Street.
The product named in the release is Aqua Reslin, EPA registration No. 432-796, applied at 0.5 ounces per acre by certified technicians. The county said the risk to people and animals from the product is very low or nonexistent but advised keeping residents and pets inside, with windows shut, for 15 minutes once spraying is done.
Murrieta-area surveillance
After the positive bird, Vector Control staff increased surveillance in the Murrieta area, looked for potential breeding sites and conducted larval control where needed, the county said.
As of the release, the county said, mosquito samples from the service area where the bird was collected had not tested positive for the virus.
"West Nile Virus has been detected in our community. 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," Third District Supervisor Chuck Washington said in the release.
The county advised residents to use repellents with one of four active ingredients — DEET, picaridin, IR3535 or oil of lemon eucalyptus — and to empty or throw out containers holding water. It also advised weekly water changes for pet bowls, troughs and birdbaths, and snug screens on doors and windows.
Mosquito activity peaks around dusk and dawn, the release said. It asked residents who are bitten during daytime hours to contact the office, because that information helps identify the mosquito species in an area.
The Vector Control office takes reports of mosquito problems and requests for mosquito-eating fish at 951-766-9454, the county said. More information is posted at rivcoeh.org/vector-control.