West Nile virus dead bird infections by county for California 2026

(2026-09-18) - Source: http://westnile.ca.gov

*Birds reported as "chronic" do not have sufficient virus to cause mortality from WNV. Similarly, these birds do NOT indicate recent WNV transmission in the county and they cannot spread WNV to mosquitoes or other animals.

Birds reported as "positive" have high levels of virus, indicating the bird was recently infected with WNV. They are an indicator of current WNV in the county.

Results are determined by molecular testing of bird tissues.

More information:

CountyPositiveChronic*Total
Alameda36036
Contra Costa11011
El Dorado101
Fresno303
Los Angeles1340134
Madera303
Merced202
Napa101
Orange86086
Placer909
Riverside909
Sacramento1050105
San Bernardino15015
San Diego44044
San Joaquin909
San Mateo909
Santa Clara1070107
Solano202
Sonoma101
Stanislaus101
Sutter303
Ventura606
Yolo18018
Yuba303
Totals: 6180618

Source: Vector-Borne Disease Section, California Department of Public Health