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 June was lower than average (343 requests compared to a five-year average of 415). Yellowjackets and other wasp requests were the furthest below average (127 compared to a five-year average of 174) but the numbers are increasing, as is typical in the summer. Yellowjacket-related service requests usually peak in August. Tick service requests were more than…
2026 Mosquito SurveillanceAdult mosquito counts rose in June, particularly the species Culex erythrothorax, which has numbers about twice as high as average. This mosquito breeds in tule marshes and ponds and the high numbers are from sites in Mills Field, near the San Francisco airport. Technicians are working to access areas where it is difficult to apply pesticides because of thick vegetation surrounding standing water…
