Skip to main content

West Nile Virus Activity 2021

May contain: nature and outdoors

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 in 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 CA state program: Dead birds help determine spread of West Nile virus
  • Sentinel Chickens – Chickens develop antibodies to West Nile virus, which can be detected by testing.

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


Year-to-Date Statistics for 2021

2021 WNV+ Mosquito Samples

City/CommunityDate of First Detection# of Positive Samples
Bellflower 7/13/20211
Studio City 7/15/2021 
Total # of Positive Mosquito Samples This Year


2021 WNV+ Dead Birds

City/CommunityDate of First Detection Positives
 Valley Village7/7/2021 1