CONCORD, CALIFORNIA – The Contra Costa Mosquito and Vector Control District (District) reports two groups of trapped mosquitoes have tested positive for West Nile virus (WNV) in Contra Costa County. The mosquitoes, Culex tarsalis, and Culex pipiens, were collected in traps in the City of Oakley this week.
In addition to the mosquitoes, there have been four dead birds that have tested positive for WNV, and five sentinel chickens have tested positive for antibodies. WNV-infected dead birds have also been reported from Alameda, San Mateo, and Santa Clara Counties, while Alameda, Santa Clara, and Solano Counties have also confirmed they have found WNV-infected mosquitoes in 2024.
“Although West Nile virus transmission can happen anywhere in Contra Costa County, the presence of WNV-positive mosquito samples, dead birds, and sentinel chickens in Oakley indicates an elevated risk currently exists for residents and visitors in that area. This makes it particularly important for people in the area to protect themselves from mosquito bites, while our staff work to reduce the risk,” said Steve Schutz, Ph.D., Scientific Program Director.
To reduce the risk in Oakley tonight, District employees will be conducting Adult Mosquito Control on the northern border of Oakley where West Nile virus evidence was found. Additional treatments may be necessary in the area.
To reduce the risk of mosquito bites, the District recommends residents use an EPA-registered insect repellent with one of the following active ingredients:
- DEET
- Picaridin
- The repellent version of Oil of Lemon Eucalyptus
- IR3535
Always follow the instructions on the label when using insect repellent.
To reduce the risk of mosquitoes on residential properties, the District recommends Contra Costa County residents look around their front and backyards at least once a week and dump out any amount of standing water. Also, check window screens to make sure they fit properly without any gaps or rips in the screen.
Contra Costa County residents can report dead birds by phone at (877) WNV-BIRD (968-2473) or online. County residents can also request mosquito service for residential property by calling (925) 685-9301 or online. Signing up for District notifications allows Contra Costa County residents to receive information on West Nile virus activity and Adult Mosquito Control operations in real-time. Subscribe to District publications here.
Previous Stories:
- Aug 9 – Tonight: Adult Mosquito Control to Take Place in Oakley
- July 26 – First West Nile Death Since 2006 Reported in Contra Costa County
- June 21 – West Nile Virus-Infected Birds Confirmed in Concord
- April 27 – First West Nile Virus Positive Dead Bird of 2024 Found in Contra Costa County
