West Nile Virus Update – May 2018

San Mateo County

As of June 3, 2019, there have been 86 dead birds reported in San Mateo County. Of those, sixteen have been suitable for testing and all sixteen 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 three counties in 2019 (see map), compared to a five year average of twelve counties at this date. Statewide, 1,777 birds have been reported and 425 have been tested with one positive result (0.008%), from San Diego County. Forty-one mosquito pools have tested positive for WNV this year, although 37 out of 41 have been from Riverside County. Orange County and Tulare County have also detected positive mosquitoes. No positive sentinel chickens or human cases have yet been reported in California.