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West Nile Virus Activity

May contain: animal, bird, and crow

Did you know West Nile virus is the most common mosquito-borne disease that affect residents in Los Angeles County?

The District surveillance staff routinely collects samples of mosquitoes from traps and have them tested for a mosquito-borne diseases. In addition, dead birds, which can carry West Nile virus, are submitted for testing.

Keep in mind that West Nile virus is endemic to Los Angeles County. This means it is found naturally in our city environments. During warmer weather, the virus activity increases, which increases the chance for our traps to catch mosquitoes carrying West Nile virus and any other viruses that can be a public health threat. 

Human cases are reported by the L.A. County Department of Public Health and Pasadena Health Department.


2019 West Nile Virus Activity


West Nile Virus Positive Mosquito Samples

A sample is a random collection of 10-50 mosquitoes from a trap

City/CommunityNumber of WNV+ Mosquito Samples
Baldwin Park1
La Verne1
West Covina1


West Nile Virus Positive Dead Birds

None reported at this time