West Nile Virus Update – June 2019

San Mateo County

As of June 28, 2019, there have been 120 dead birds reported in San Mateo County. Of those, 23 have been suitable for testing and all 23 have tested negative for West Nile virus (WNV). No mosquito pools or sentinel chickens have tested positive for West Nile virus in San Mateo County in 2019.

The District asks residents to report dead birds. Specimens that appear to have been dead for less than 24 hours and are in good condition will be tested for WNV.  Residents should contact the state WNV hotline at 877-WNV-BIRD (968-2473). Reports can also be made online at


WNV has been detected in eight counties in 2019 (see map), compared to a five year average of 21 counties at this date. Statewide, 2,444 birds have been reported and 671 have been tested with five positive results (1%). All five positive birds were from southern California counties.  Seven counties throughout California have detected 220 WNV positive mosquito samples. None of the positive mosquito samples have been from the Bay Area coastal region. No positive sentinel chickens or human cases have yet been reported in California.