CA Dept. of Public Health UC Davis Arbovirus Research and Training Mosquito and Vector Control Assoc. of CA

Case Counts by County

CountyDead birds
Alameda11
Alpine-
Amador-
Butte22
Calaveras-
Colusa-
Contra Costa33
Del Norte-
El Dorado4
Fresno6
Glenn4
Humboldt-
Imperial-
Inyo-
Kern-
Kings4
Lake5
Lassen-
Los Angeles124
Madera5
Marin5
Mariposa-
Mendocino-
Merced5
Modoc-
Mono-
Monterey-
Napa1
Nevada2
Orange89
Placer30
Plumas-
Riverside16
Sacramento411
San Benito-
San Bernardino5
San Diego264
San Francisco-
San Joaquin37
San Luis Obispo-
San Mateo15
Santa Barbara-
Santa Clara89
Santa Cruz2
Shasta3
Sierra-
Siskiyou-
Solano13
Sonoma8
Stanislaus14
Sutter10
Tehama-
Trinity-
Tulare3
Tuolumne-
Ventura34
Yolo72
Yuba4
Total1350

WNV Activity by County
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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).

Having problems with mosquitoes?

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Compared to previous year and previous five-year average to date

As of Dec 09, 2016201620155Y AVG
Counties394140
Human cases411702488
Dead birds135013401470
Mosquito samples351433292826
Sentinel chickens343449461
YTD - Year to date corresponds to the same time last year or last five years.

- view all 2015 YTD activity -

WNV Reports

Weekly Report

12.09 2016 YTD WNV Activity Map
12.06 2016 US Arboviral Activity Update
12.02 Arbovirus Bulletin #38

Humans

12.02 2016 Human WNV Incidence Report
11.16 2003-2016 WNV Case Summary
03.21 2015 Human WNV Incidence Report

Dead Birds

12.09Positive Species for 2016
12.09Reported, Tested, Positive 2016
12.09Positive Counts by City/County for 2016

Mosquitoes

11.10 AMOR - EVS Week 44
11.10 AMOR - GRAVID Week 44
11.10 AMOR - NJLT Week 44
- view report archives -