The Contra Costa Mosquito and Vector Control District confirmed that more groups of mosquitoes have tested positive for West Nile virus in Contra Costa County.
The mosquitoes were collected from traps on Holland Tract and an agricultural area east of Brentwood.
The findings mean that one dead bird and seven groups of mosquitoes have now tested positive for West Nile virus this year in Contra Costa County, officials said.
Certain birds carry the virus. Mosquitoes can become infected by biting an infected bird, then spreading the virus by biting another bird or person.
Seventy-three people have been diagnosed with West Nile virus in Contra Costa County since 2005. Two people died from the disease in 2006.
To reduce the risk of transmission of the virus, the district recommends that Contra Costa County residents report dead birds, as they are often the first sign of a virus outbreak in a particular location.
The district also urges county residents to dump out any amount of standing water to reduce the risk of attracting mosquitoes.
"Mosquitoes develop from egg to biting adult in water, even small amounts of water,” said Steve Schutz, scientific program manager. “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 (the virus). The risk of (the virus) does not truly diminish until nights become chilly.”
According to the Centers for Disease Control and Prevention, Environmental Protection Agency, (EPA)-registered insect repellents have been proven safe and effective when used as directed. The Contra Costa Mosquito and Vector Control District recommends using EPA-registered insect repellents with one of the following active ingredients: DEET, Picaridin or Oil of Lemon Eucalyptus.
Contra Costa Mosquito and Vector Control District officials remind all insect repellent users to follow the instructions on product labels.
Contra Costa County residents are encouraged to report dead birds by phone at 877- WNV-BIRD (968-2473).
County residents can also request mosquito treatment service for residential properties by calling 925-685-9301.