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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/Community   Date of First Detection# of Positive Samples
Canoga Park8/25/20212
Downtown LA8/13/20211
Elysian Valley7/22/20211
Hacienda Heights8/4/20213
Highland Park9/2/20211
La Mirada8/26/20211
Long Beach8/25/20212
Mission Hills8/13/20211
San Marino 8/17/20211
Santa Clarita 8/20/20211
Santa Fe Springs8/26/20212
Silver Lake9/9/20211
South El Monte8/4/20212
South Whittier9/15/20211
Studio City 7/15/2021 2
Valley Glen8/12/20211
Valley Village7/28/20213
Van Nuys8/18/20212
Woodland Hills8/11/20214
Total # of Positive Mosquito Samples This Year53


2021 WNV+ Dead Birds

City/CommunityDate of First Detection Positives
Long Beach 7/13/2021 2
Valley Village7/7/2021 1
Total # of Positive Dead Birds this Year7