Dead Birds Reported, Tested, and Positive
for WNV by County in California in 2021
Year To Date (Weeks 1 - 53)

(2022-12-09) - Source: http://westnile.ca.gov

CountyReported*TestedPositive% Tested Positive
Alameda2907723%
Alpine----
Amador6---
Butte3211218%
Calaveras4---
Colusa2---
Contra Costa39237411%
Del Norte1---
El Dorado378--
Fresno918--
Glenn4---
Humboldt1---
Imperial1---
Inyo1---
Kern274--
Kings9---
Lake64--
Lassen----
Los Angeles7621334332%
Madera62--
Marin392--
Mariposa1---
Mendocino5---
Merced352150%
Modoc----
Mono----
Monterey137--
Napa268--
Nevada207229%
Orange55343572%
Placer12052510%
Plumas----
Riverside10826--
Sacramento71240310025%
San Benito51--
San Bernardino1112614%
San Diego1377611%
San Francisco378--
San Joaquin133541731%
San Luis Obispo268--
San Mateo30278--
Santa Barbara3610--
Santa Clara4539311%
Santa Cruz6618--
Shasta191--
Sierra----
Siskiyou1---
Solano652428%
Sonoma969111%
Stanislaus12414214%
Sutter277114%
Tehama2---
Trinity1---
Tulare4814750%
Tuolumne21--
Ventura481417%
Yolo162701014%
Yuba203--
State Totals5225175521012%

* Birds in a die-off are not included in reported totals because the deaths are not related to WNV. A die-off is defined as a group of 10 or more same species dead birds unless the species is American Crow.
Source: Vector-Borne Disease Section, California Department of Public Health