Mosquitoes Collected in South San Francisco Not Infected with West Nile Virus

On April 2nd, a dead American crow collected in South San Francisco tested positive for West Nile virus. This is the second dead bird positive for West Nile virus found in San Mateo County in 2018. The first was collected in February in Foster City.

To check for risk of local transmission, the laboratory staff will set mosquito traps in the area where the crow was found. These mosquitoes were tested yesterday at the District laboratory, and we did NOT find any sign of West Nile virus. Since WNV can only be transmitted to people by the bite of an infected mosquito, this means that the human health risk posted by WNV remains low in this area.

However, it’s important to keep an eye out for dead birds, and report any you find to the District. If you find one, give us a call at (650) 344-8592. Carcasses that are in good condition and appear to have been dead less than 24 hours can be tested for WNV.

The risk of West Nile virus in an area can change quickly, so you should continue to prevent mosquitoes around your home and take precautions against mosquito bites when spending time outdoors.

Other questions about WNV? Check out our FAQ.