West Nile virus in Contra Costa mosquitoes
Residents urged to use repellent, report neglected swimming pools
Mosquitoes infected with West Nile virus have been discovered in Contra Costa County several times this month, prompting officials to warn residents.
The disclosure comes one week after California recorded its first West Nile virus death of the year in San Luis Obispo County.
Mosquitoes with the virus have been collected from traps in agricultural areas near Byron and Brentwood at the eastern edge of the county, according to the Contra Costa Mosquito and Vector Control District. Entomologists tested insect samples for the disease, which is transmitted to humans by a bite from an infected mosquito.
“It only takes one bite, from one mosquito,” said Nola Woods, the agency’s spokesperson.
West Nile virus is on the rise in California, state public health officials said after the death. In addition to two cases of human infection, the virus had been found in 68 dead birds from six counties and in 283 mosquito samples as of Friday, according to state tallies.
More than 7,000 cases have been reported since the virus first appeared in the state nearly two decades ago, with 73 cases in Contra Costa County. Two county residents died from the disease in 2016.
The county has discovered West Nile virus in birds and mosquitoes every year since 2005, Woods said.
While 20% of people with West Nile virus exhibit no symptoms, another 20% of those infected experience body aches and nausea within days or weeks of being bitten by a viruscarrying mosquito.
Woods urged residents to wear insect repellent when outdoors and to dump standing water — a common breeding ground for mosquitoes. Neglected swimming pools are among the biggest risks, Woods said, and can produce up to 1 million new mosquitoes in a season if not properly tended.
“One neglected swimming pool can impact an entire community,” she said.
Residents can report neglected swimming pools on the agency’s website and are encouraged to report dead birds, which can be carriers of the virus, by calling (877) 9682473.
Additionally, residents with backyard ponds or other decorative water features may be eligible to receive mosquito-eating fish through a county program, Woods said.