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West Nile Virus Activity 2025

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 2025

2025 WNV+ Mosquito Samples

City/CommunityDate of First DetectionPositives
Arleta6/30/20252
Artesia7/22/20252
Bellflower7/17/20252
Burbank9/19/20256
Canoga Park8/28/20251
Carson8/12/20252
Cerritos 9/17/20251
Downey8/14/20251
Encino8/21/20255
Gardena 9/9/20251
Glassell Park9/4/20251
Granada Hills7/22/20256
Hawaiian Gardens9/5/20251
Hollywood Hills9/9/2025 1
Lake Balboa9/15/202512
Lakewood8/1/20254
Los Angeles - South Park 9/12/20251
Los Angeles - South Central9/12/20251
Mission Hills7/15/20252
Montebello 9/11/20251
North Hills8/8/20253
North Hollywood9/9/20252
Northridge7/30/20253
Norwalk8/20/20254
Pacoima9/30/20251
Panorama City7/8/20258
Pico Rivera 9/17/20251
Porter Ranch9/15/20251
Reseda8/13/20255
 Santa Fe Springs9/17/20252
Sherman Oaks8/8/20259
South El Monte7/2/20251
Studio City7/25/20258
Sun Valley8/12/20253
Tarzana8/27/20251
Toluca Lake8/26/20252
Valley Glen6/30/202512
Valley Village7/15/2025 10
Van Nuys 7/8/20258
West Hills8/14/20251
Wilmington 9/23/20251
 Total139

2025 WNV+ Dead Birds

City/CommunityDate of First DetectionPositives
North Hollywood9/11/20251
Norwalk 9/8/20251
Sherman Oaks 7/17/20251
Total 3

 

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.