Skip to main content

Current West Nile Virus Information for San Mateo County

2023 Season

October typically marks the end of the West Nile virus season. The California state West Nile virus hotline closed live operator service on October 13, 2023. However, residents can continue to report dead birds online at District staff will collect and test suitable birds through the winter months. For information about West Nile virus throughout the state, please visit:


San Mateo County

In 2023, no mosquito pools tested positive for West Nile virus in San Mateo County. No sentinel chickens tested positive for West Nile virus.  For information about West Nile virus in humans and horses, visit: or

In 2023, a total of 14 dead birds tested positive for West Nile virus in San Mateo County. Positive birds were found in Belmont (1), Burlingame (1), Foster City (1), Redwood City (1 in Redwood City; 3 in Redwood Shores area; 2 on the border of Redwood City and North Fair Oaks), San Carlos (1), and Menlo Park (4). Additional mosquito trapping and testing done in areas where dead birds were found did not found any positive mosquitoes.

For tips on how to avoid mosquito bites and select a safe, effective mosquito repellent, click HERE.



Page last reviewed: December 1, 2023

Join our mailing list