West Nile Virus in Los Angeles County

West Nile Virus is the most common mosquito-borne disease that affects residents in Los Angeles County. Public health agencies detect West Nile virus every year in L.A. County, which means it's endemic and found naturally in our city environments.

Our agency reports data related to mosquitoes. Human cases are reported by the L.A. County Department of Public Health.

The disease surveillance program serves as an early warning system for the detection of mosquito-borne viruses that can infect people and animals.

The District uses the following factors to assess health risk in your community:

• Higher-than-average daily temperatures
• Mosquito Population Monitoring – Using traps set up in every community
• Mosquito Testing for Diseases
• Dead Birds – A California state program: Dead birds help determine the spread of West Nile virus

Using these measurements, the District is able to protect your health by responding appropriately to mosquito-borne disease threats.

We could also use your help! If you see any dead birds in your community, please report them to the California Department of Public Health by completing an online report at https://westnile.ca.gov/report or by calling 1-877-WNV-BIRD.

 

Year-to-Date Statistics for 2026

 

Take a look at mosquito and disease activity throughout California by utilizing the VectorSurv map! 

Visit the full site here.

 

Did you know Los Angeles County is serviced by five vector control districts?

Visit our Other Agencies page to find your local vector control district.