West Nile Virus Activity 2021

West Nile virus Facts

West Nile virus is the most common mosquito-borne disease that affect 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 colect samples of mosquitoes. The mosquito samples are tested for a mosquito-borne diseases, such as West Nile virus. In addition, dead birds, which can carry West Nile virus, are submitted for testing.

Our agency reports data related to mosquitoes. Human cases are reported by the L.A. County Department of Public Health and Pasadena Health Department.

2021 West Nile Virus Activity

Last update: 10/22/2021

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 of the spread of West Nile virus.

City/Community	Number of WNV+ Mosquito Samples	Date of first report
Alhambra	10	8/6
Arcadia	4	9/13
Azusa	9	7/22
Baldwin Park	10	7/22
Claremont	1	8/6
Covina	23	6/28
Duarte	1	7/22
El Monte	2	10/4
Glendora	11	7/12
Industry	2	8/12
Irwindale	5	7/12
La Puente	4	8/27
La Verne	6	7/30
Monrovia	1	9/20
Monterey Park	2	9/20
Pasadena	10	7/22
Pomona	3	9/2
Rosemead	7	7/30
San Dimas	14	7/19
San Gabriel	4	9/20
South Pasadena	11	7/19
Temple City	5	8/27
Unincorporated LA County (Charter Oak)	2	10/4
Unincorporated LA County (Mayflower Village)	2	10/4
Unincorporated LA County (Vincent neighborhood)	6	6/21
Unincorporated LA County (West Puente Valley neighborhood)	2	7/12
Walnut	8	7/22
West Covina	25	6/21
TOTAL	190	--