Dead Birds Reported, Tested, and Positive
for WNV by County in California in 2009
Year To Date (Weeks 1 - 28)

(2025-07-16) - Source: http://westnile.ca.gov

CountyReported*TestedPositive% Tested Positive
Alameda41439615%
Alpine1---
Amador402--
Butte38129310%
Calaveras442--
Colusa305240%
Contra Costa12219255%
Del Norte11---
El Dorado2832115%
Fresno9771213731%
Glenn955--
Humboldt326--
Imperial30---
Inyo223--
Kern617611525%
Kings15222627%
Lake393133%
Lassen71--
Los Angeles20142012814%
Madera10812650%
Marin147---
Mariposa283--
Mendocino496--
Merced3037114%
Modoc133133%
Mono71--
Monterey1478--
Napa912--
Nevada9611--
Orange86222263%
Placer4022814%
Plumas25---
Riverside3641218%
Sacramento142311055%
San Benito264--
San Bernardino5245436%
San Diego453781418%
San Francisco838--
San Joaquin5816857%
San Luis Obispo14314--
San Mateo1782514%
Santa Barbara632150%
Santa Clara62863711%
Santa Cruz1691318%
Shasta26636514%
Sierra----
Siskiyou61--
Solano2621--
Sonoma230---
Stanislaus5944649%
Sutter634--
Tehama519--
Trinity10---
Tulare3925148%
Tuolumne335120%
Ventura2652414%
Yolo3102215%
Yuba171--
State Totals15822156717311%

* 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