The infected bird, a Western scrub jay, was found near the intersection of Candlestick and Silverado drives, Contra Costa Mosquito and Vector Control District spokeswoman Deborah Bass said.
Although high-risk areas change daily depending on how many dead birds are reported to the state's West Nile virus hotline, an area in Antioch bordered roughly by state Highway 4, Deer Valley Road, Empire Mine Road and Somersville Road has been considered a high-risk area for the past couple of weeks, Bass said.
East County tends to have higher populations of infected mosquitoes than West County, in part because warmer temperatures speed up mosquito life cycles and increase production of the virus in their salivary glands, Bass said.
Mosquito district personnel have been scouring the area emptying catch basins and looking for standing water where mosquitoes could be laying eggs. Destroying mosquito larva before they hatch is the most effective way to control populations, said Bass.
Because of the high number of housing foreclosures in the county, the mosquito district has also hired three people to find and treat abandoned swimming pools, Bass said.
The bird found Monday was the second bird to test positive for the virus in Contra Costa County this year. The first bird was found in Alamo in May.
Mosquitoes collected from Holland Tract have also tested positive for the virus, but no human cases have been documented so far.
Since the virus was first detected in the county in 2004, 22 people have been diagnosed with the disease and two have died from it.
Although most people bitten by an infected mosquito will not get sick and some will only come down with mild flu-like symptoms, the illness can cause more severe symptoms, including paralysis or death, and the mosquito district is urging people to protect themselves against mosquito bites.
People should remove sources of standing water, make sure their door and window screens are in good repair and wear insect repellant if they are going to be exposed to mosquitoes, particularly at dawn and dusk when the insects are most active.
To help the mosquito district identify areas with high numbers of infected mosquitoes, people are also asked to report dead birds to the state by calling (877) WNV-BIRD.
Not all dead birds will be picked up and tested, but reports will be used to determine higher-risk areas, which tells local mosquito control districts where to concentrate their mosquito abatement efforts, Bass said.
