Mosquitoes found in two locations in eastern Contra Costa County have tested positive for West Nile virus, county officials said Thursday.
The infected mosquitoes were found in traps in Discovery Bay and in an agricultural area east of Brentwood and come less than a week after chickens near Knightsen tested positive for antibodies against the virus, according to the Contra Costa Mosquito and Vector Control District.
"We are seeing a typical summer pattern where West Nile virus activity starts in the warmer areas of the Central Valley and gradually moves west into Contra Costa County as our weather warms up," the district's scientific programs manager Steve Schutz said in a statement.
District officials encourage people to reduce their risk of contracting West Nile virus by using insect repellents, avoiding the outdoors during dusk and dawn when mosquitoes are most often present, and getting rid of standing water where mosquitoes breed.
Residents are also encouraged to report dead birds, which can be a sign of West Nile virus. Anyone who finds a dead bird is asked to call (877) WNV-BIRD.
Since 2005, 63 county residents have been diagnosed with West Nile virus, and two people died from the disease in 2006.