West Nile Virus

Mosquito closeup biting humanWest Nile Virus season is here.

While there have been no reported human cases of West Nile virus in San Mateo County, it's best to practice good prevention and fight the mosquito bite.  Although most people who become infected with the virus never develop any symptoms, some people may develop a more serious illness, such as meningitis or encephalitis. WNV is a seasonal epidemic in North America that flares up in the summer and continues into the fall. For more information about West Nile Virus, visit WestNile.ca.gov.

West Nile virus in the U.S.

Since 1999, more than 30,000 people in the United States have been reported sick with West Nile virus, which is spread by infected mosquitoes. In the U.S., there have been a total of nearly 700 human cases of West Nile virus disease this year, and 26 deaths related to the virus.  This is the highest number of reported cases since West Nile virus was first detected in 1999.  Most cases have been reported from six states, including California.  For maps and statistics of WNV in the United States, visit the CDC's information page.

West Nile virus in California

In California, there have been 275 human cases of West Nile virus reported so far this year in 26 counties. Seven WNV-related deaths have been reported. At this time last year, there were a total of 298 human cases reported in California. For the most current update, visitwww.westnile.ca.gov.

There have been no reported human cases of West Nile virus in San Mateo County.

San Mateo County has a Mosquito Control Program

The San Mateo County Mosquito and Vector Control District is San Mateo County’s community-based mosquito control program (www.smcmad.org). This program uses different methods to help control the risk of disease in San Mateo County, including surveillance, prevention, and control of mosquito populations.

To report a dead bird or squirrel, click here for the reporting website.

Vector Control does extra mosquito monitoring in neighborhoods where positive birds and squirrels are found. All mosquitoes that were trapped and tested in San Mateo County so far this year have tested negative for the virus.

Here’s what you can do to help control West Nile virus:

  • Mosquitoes are most active at dusk and dawn so be sure to use insect repellent, and consider staying indoors or wear long sleeves and pants during these times.
  • Make sure you have good screens on your windows and doors to keep mosquitoes out.
  • Get rid of mosquito breeding areas by emptying standing water from anything that collects water (such as containers, flower pots, pet food and water dishes, swimming pool covers, buckets, etc.). You can also report abandoned swimming pools by calling (650) 344-8592.
  • Report dead birds and squirrels by completing a report at www.westnile.ca.gov.

For more details about West Nile virus, prevention, what insect repellents to use, and other important information, visit the California West Nile Virus Website.