West Nile Virus Update
May 2018

San Mateo County

As of May 25, 2018, there have been 115 dead birds reported in San Mateo County. Of those, 25 have been suitable for testing and two have tested positive (8%) for West Nile virus (WNV). No mosquito pools or sentinel chickens have tested positive for West Nile Virus in San Mateo County in 2018.

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 six counties in 2018 (see map), compared to a five year average of ten counties at this date. Statewide, 1737 birds have been reported and 338 have been tested with seven positive results (3%). Two mosquito pools have tested positive for WNV this year, one from San Bernardino County and one from Alameda County. No positive sentinel chickens or human cases have yet been reported in California.