Case Counts by County

CountyDead birds
Alameda62
Alpine-
Amador-
Butte18
Calaveras-
Colusa4
Contra Costa28
Del Norte-
El Dorado1
Fresno8
Glenn4
Humboldt2
Imperial-
Inyo-
Kern3
Kings2
Lake14
Lassen-
Los Angeles31
Madera4
Marin3
Mariposa-
Mendocino-
Merced-
Modoc-
Mono-
Monterey-
Napa9
Nevada-
Orange209
Placer23
Plumas-
Riverside-
Sacramento238
San Benito-
San Bernardino8
San Diego4
San Francisco-
San Joaquin36
San Luis Obispo-
San Mateo8
Santa Barbara-
Santa Clara730
Santa Cruz1
Shasta2
Sierra-
Siskiyou-
Solano31
Sonoma13
Stanislaus31
Sutter19
Tehama-
Trinity-
Tulare38
Tuolumne-
Ventura2
Yolo46
Yuba11
Total1643

WNV Activity by County
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2014 | 2013 | 2012
2011 | 2010 | 2009
2008 | 2007

Press Releases

CDPH Reports First Human West Nile Virus Case of 2012

Jun 18, 2012

SACRAMENTO - A 70-year-old female in Kern County is the first confirmed human case of West Nile virus infection in California this year, announced Dr. Ron Chapman, state health officer and director of the California Department of Public Health (CDPH). The woman was hospitalized, but is now recovering.

"This first confirmed West Nile virus case reminds us that we must take precautions to protect ourselves and our families from mosquito bites," said Chapman. "West Nile virus activity is greatest during the summertime."

West Nile virus is transmitted to humans and animals by the bite of an infected mosquito. The risk of serious illness to most people is low. However, some individuals - less than 1 percent - can develop a serious neurologic illness such as encephalitis or meningitis. People 50 years of age and older have a higher chance of getting sick and are more likely to develop complications. Recent data also indicates that those with diabetes and/or hypertension are at greatest risk for serious illness.

To date in 2012, West Nile virus has been detected in 15 California counties.

CDPH recommends that individuals prevent exposure to mosquito bites and West Nile virus by practicing the "Three Ds":


  1. DEET - Apply insect repellent containing DEET, picaradin, oil of lemon eucalyptus or IR3535 according to label instructions. Repellents keep the mosquitoes from biting you. DEET can be used safely on infants and children 2 months of age and older.
  2. DAWN AND DUSK - Mosquitoes bite in the early morning and evening so it is important to wear proper clothing and repellent if outside during these times. Make sure that your doors and windows have tight-fitting screens to keep mosquitoes out. Repair or replace screens with tears or holes.
  3. . DRAIN - Mosquitoes lay their eggs on standing water. Eliminate all sources of standing water on your property, including flower pots, old car tires, rain gutters and pet bowls. If you know of a swimming pool that is not being properly maintained, please contact your local mosquito and vector control agency.

California's West Nile virus website includes the latest information on West Nile virus activity in the state. Californians are encouraged to report all dead birds and dead tree squirrels on the website or by calling toll-free 1-877-WNV-BIRD (968-2473).

Locate Your Local Mosquito and Vector Control Agency
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Compared to previous year and previous five-year average to date

As of Aug 27, 2014201420135Y AVG
Counties364134
Human cases1298646
Dead birds1643907572
Mosquito samples230515621175
Sentinel chickens184231142
YTD - Year to date corresponds to the same time last year or last five years.

- view all 2013 YTD activity -

WNV Reports

Weekly Report

08.27 2014 YTD WNV Activity Map
08.26 2014 US Arboviral Activity Update
08.22 Arbovirus Bulletin #27

Humans

08.25 2014 Human WNV Incidence Report
08.25 2003-2014 WNV Case Summary
08.12 2013 Human WNV Incidence Report

Dead Birds

08.27Reported, Tested, Positive 2014
08.27Positive Counts by City/County for 2014
08.27Positive Species for 2014

Mosquitoes

08.22 AMOR - EVS Week 33
08.22 AMOR - GRAVID Week 33
08.22 AMOR - NJLT Week 33
- view report archives -