08/11/2026
WEST NILE VIRUS INCREASES IN CONTRA COSTA COUNTY
So far, the majority of the activity is in El Cerrito
CONCORD, CALIFORNIA - The Contra Costa Mosquito and Vector Control District (District) confirms seven birds and one group of mosquitoes have tested positive for West Nile virus (WNV) so far this year. Of the seven birds, four are from El Cerrito. Since the District first found WNV in Contra Costa County, El Cerrito has been the site of only one previous bird that tested positive in 2023.
“Finding four West Nile virus-positive dead birds in El Cerrito is significant because we have not previously detected this level of activity in the area,” said Dr. Paula Macedo, General Manager. “This cluster of detections underscores the importance of continued surveillance and reminds residents to take precautions to prevent mosquito bites and eliminate standing water around their homes.”
Mosquitoes typically become infected with WNV after biting an infected bird. Dead bird reports to the California West Nile Virus Call Center provide important information to the District, as dead birds are often the first sign of WNV in a particular location.
What is the District Doing in Response to the WNV-Infected Birds in El Cerrito?
In response to the number of infected birds in El Cerrito, District employees are setting traps in the area where the birds have been reported. So far, the traps have not collected any infected mosquitoes, but the trapping will continue. District employees are also performing inspections and treatment of known sources of mosquito production in the area.
What Do Residents Need to Do with WNV Activity Nearby?
El Cerrito residents should put on mosquito repellent before going outside in the morning and evening, as mosquitoes that transmit WNV are most active at those times. Repellents with the following ingredients are most effective:
DEET
Picaridin
The repellent version of Oil of Lemon Eucalyptus
IR3535
Always follow the instructions on the label when using insect repellent.
In addition to putting on mosquito repellent, to reduce the risk of mosquitoes on their own properties, the District recommends Contra Costa County residents walk around their front and back yards at least once each week and dump out any amount of standing water to remove locations where mosquitoes can be produced.
Contra Costa County residents may contact the District to request mosquito service by calling (925) 685-9301 or online. Contra Costa County residents pay for District services through property taxes, so there is no additional charge for county residents to request a District service.
Contra Costa County residents can report dead birds by phone at (877) WNV-BIRD (968-2473) or online.
