West Nile Virus Update
June 2018

San Mateo County

As of June 29, 2018, there have been 176 dead birds reported in San Mateo County. Of those, 52 have been suitable for testing and two have tested positive (4%) 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 15 counties in 2018 (see map) compared to a five year average of 22 counties at this date. Statewide, 3013 birds have been reported and 687 have been tested with seven positive results (5%). 31 mosquito pools have tested positive for WNV this year. In the San Francisco Bay Area, mosquito control districts in Alameda County and Santa Clara County fogged for adult mosquitoes in June, following WNV positive mosquito detections. Throughout California, there have been nine human cases of WNV, compared to a five-year average of one at this date. No positive sentinel chickens have yet been reported in California.