Mosquitoes with West Nile virus were detected for the first time this year in Napa County on Friday, according to county officials.
The mosquitoes were found in two samples in American Canyon.
Napa County is the eighth and latest Bay Area county where the virus has been detected in birds, mosquitoes or chickens.
The only Bay Area county where the virus has not been found in San Francisco.
The chance of becoming seriously ill from the virus is low. The virus is transmitted to humans and animals through a bite from an infected mosquito, county officials said.
Health officials recommend people protect themselves from mosquito bites by applying insect repellent with DEET, picaradin, oil of lemon eucalyptus or IR3535.
The officials suggest people be especially careful by wearing proper clothing and insect repellent at dawn and dusk when mosquitoes are most active.
Also, residents should consider eliminating standing water in places such as rain gutters, old tires and pet bowls. Mosquitoes lay their eggs on water, county officials said.
Anyone aware of a neglected swimming pool or for other mosquito problems, residents are encouraged to call the Napa County Mosquito Abatement District at (707) 553-9610.