CONCORD, CALIFORNIA - The Contra Costa Mosquito & Vector Control District (District) reports two more groups of mosquitoes have tested positive for West Nile virus (WNV) in Contra Costa County.

The mosquitoes were collected from traps on Holland Tract and an agricultural area east of Brentwood. Both locations are in eastern Contra Costa County. There are now one dead bird and seven groups of mosquitoes that have tested positive for WNV so far this year in Contra Costa County.

Certain birds carry WNV. Once a mosquito bites an infected bird, the mosquito can become infected. Mosquitoes can spread the virus when they bite another bird or person. To reduce the risk of WNV, the District recommends Contra Costa County residents report dead birds because dead birds are often the first sign of WNV in a particular location.

With more mosquitoes testing positive for WNV in Contra Costa County, along with the small amount of rain the county received Thursday night into Friday morning, the District urges county residents to dump out any amount of standing water to reduce the risk of mosquitoes.

"Mosquitoes develop from egg to biting adult in water, even small amounts of water. That's why it is very important for Contra Costa County residents to dump out any amount of water that collected in buckets, toys, tools, and any other outdoor containers during the recent rain. Even an amount as small as a bottle cap full of water can produce mosquitoes. And it is especially important to reduce the risk of mosquitoes in late summer and early fall because this is the time of year when we typically see the largest number of human cases of WNV. The risk of WNV does not truly diminish until nights become chilly," said Steve Schutz, Ph.D., Scientific Program Manager.

In areas where county residents experience mosquitoes, the District recommends residents use an EPA-registered insect repellent with one of the following active ingredients:

Always follow the instructions on the label when using insect repellent.

Contra Costa County residents can request the District's mosquito service for residential property by calling (925) 685-9301 or online. County residents can also report dead birds by phone at (877) WNV-BIRD (968-2473) or online.

Contra Costa Mosquito & Vector Control District, an independent special district and public health agency, is located at 155 Mason Circle in Concord. Contact the District to report mosquito problems online or at (925) 685-9301.