Dead Birds Reported, Tested, and Positive
for WNV by County in California in 2007
Year To Date (Weeks 1 - 28)

(2025-07-10) - Source: http://westnile.ca.gov

CountyReported*TestedPositive% Tested Positive
Alameda10657423%
Alpine6---
Amador11214--
Butte10456435%
Calaveras20819211%
Colusa501--
Contra Costa204216853%
Del Norte467--
El Dorado44140--
Fresno20101403626%
Glenn158281036%
Humboldt14715--
Imperial111--
Inyo47---
Kern18881084844%
Kings1911616%
Lake14512--
Lassen848--
Los Angeles251824731%
Madera15818--
Marin45534--
Mariposa497--
Mendocino11512--
Merced48435514%
Modoc191--
Mono60---
Monterey34930--
Napa139---
Nevada3262414%
Orange83310798%
Placer100243--
Plumas818--
Riverside6492314%
Sacramento598512054%
San Benito5612--
San Bernardino7956734%
San Diego87411865%
San Francisco16116--
San Joaquin158129517%
San Luis Obispo32225--
San Mateo58565--
Santa Barbara20811--
Santa Clara19981122522%
Santa Cruz35739--
Shasta808661320%
Sierra132--
Siskiyou342--
Solano6027114%
Sonoma84985--
Stanislaus14651214235%
Sutter2555120%
Tehama1992015%
Trinity602--
Tulare5722913%
Tuolumne14610110%
Ventura62870--
Yolo6484312%
Yuba1208113%
State Totals36254238823210%

* 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