West Nile Virus Activity 2023
West Nile virus Facts
- 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. This means the virus is found naturally in our city environments, which means it's endemic.
- Our agency uses routine traps to collect samples of mosquitoes. The mosquito samples are tested for mosquito-borne diseases, such as West Nile virus. In addition, dead birds, which can carry West Nile virus, are submitted for testing.
2023 West Nile Virus Activity
West Nile Virus Positive Mosquito Samples
A sample is a random collection of 10-50 mosquitoes from a trap. Positive mosquito samples from routine and randomized trapping provide insight into the spread of West Nile virus.
| City/Community | Date of First Detection | Positives |
|---|---|---|
| Alhambra | 06/21/23 | 3 |
| Altadena | 08/17/23 | 1 |
| Arcadia | 09/13/23 | 1 |
| Azusa | 07/06/23 | 6 |
| Baldwin Park | 08/02/23 | 3 |
| Bradbury | 08/01/23 | 4 |
| Charter Oak | 06/22/23 | 6 |
| Claremont | 08/01/23 | 14 |
| Covina | 06/08/23 | 59 |
| Duarte | 08/15/23 | 1 |
| East San Gabriel | 08/01/23 | 1 |
| Glendora | 06/22/23 | 22 |
| Irwindale | 08/08/23 | 5 |
| La Puente | 08/30/23 | 7 |
| La Verne | 08/01/23 | 15 |
| Monrovia | 10/26/23 | 1 |
| Monterey Park | 09/06/23 | 5 |
| Pasadena | 07/25/23 | 5 |
| Pomona | 07/25/23 | 16 |
| Rosemead | 08/15/23 | 5 |
| San Dimas | 08/01/23 | 10 |
| San Gabriel | 09/12/23 | 5 |
| Sierra Madre | 07/11/23 | 3 |
| South Monrovia Island | 09/26/23 | 1 |
| South Pasadena | 07/25/23 | 1 |
| Temple City | 07/18/23 | 2 |
| Vincent | 06/20/23 | 3 |
| Walnut | 07/25/23 | 12 |
| West Covina | 07/20/23 | 28 |
| Total # of Positive Mosquito Samples this Year | 245 |
West Nile Positive Dead Birds Dead Birds
People report dead birds they observe in their community. Positive dead birds are an indication West Nile virus is widespread in the region.
| City/Community | Date of First Detection | Positives |
|---|---|---|
| Covina | 06/02/23 | 10 |
| Glendora | 08/31/23 | 1 |
| La Verne | 09/26/23 | 1 |
| Pomona | 09/21/23 | 1 |
| San Dimas | 08/31/23 | 1 |
| Temple City | 08/15/23 | 1 |
| Total # of Positive Dead Birds This Year | 15 |
Take a look at mosquito disease activity throughout California using the VectorSurv Map!
To experience the entire site, visit: VectorSurv.org
