West Nile Virus SurveillanceThe District’s West Nile virus surveillance program reports several types of positive West Nile virus results, including dead birds, mosquito samples (“pools”), sentinel chickens, and human cases.
Tick-borne disease pathogens in San Mateo CountyOver the past several years, staff have collected more than 30,000 ticks from around the County. Our laboratory staff identify and test these ticks for:
2026 Service RequestsThe total number of service requests in April was lower than average (276 requests compared to a five-year average of 314). In particular, mosquito-related requests dropped from March to April, probably because many of the requests for mosquito control in March were seasonal non-biting midges emerging from lagoons and other waterways around the bay. Other categories were slightly below average…
2026 Mosquito SurveillanceIn April, adult mosquito counts for several species continued their expected spring increase. Collection levels of Aedes washinoi were well above average, with 9.3 mosquitoes per trap compared to a five-year average of 2.7. A series of late rains led to increased breeding of this species in difficult-to-reach impounds and ponds in Mills Field, near San Francisco International Airport. April is…
