Test results came back negative for the presence of mosquitoes carrying the West Nile virus in the vicinity of the intersection of Alpine and Los Trancos roads in Portola Valley, according to a July 19 statement from Town Hall.
The San Mateo County Mosquito and Vector Control District trapped mosquitoes for a day following the July 18 announcement that a carcass of a dead bird found in the area was infected with the virus.
While West Nile is a disease that primarily affects birds, authorities say that it is potentially dangerous to humans, horses and other animals. Transmission requires a bite from an infected mosquito. It is not contagious.
Authorities from the district are urging residents to continue with mosquito-avoidance behavior, including eliminating sources of standing water, wearing protective clothing when outside at dawn or dusk, using tight-fitting screens to keep mosquitoes out of the house, and using repellents with label instructions that say they contain DEET, picaradin, oil of lemon eucalyptus or IR3535.
Residents should report fresh carcasses of dead birds and tree squirrels to the California West Nile Virus Hotline or by phone at 877-WNV-BIRD (877-968-2473).