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

Case Counts by County

CountyDead birds
Alameda-
Alpine-
Amador-
Butte-
Calaveras-
Colusa-
Contra Costa-
Del Norte-
El Dorado-
Fresno-
Glenn-
Humboldt-
Imperial-
Inyo-
Kern-
Kings-
Lake-
Lassen-
Los Angeles1
Madera-
Marin-
Mariposa-
Mendocino-
Merced-
Modoc-
Mono-
Monterey-
Napa-
Nevada-
Orange1
Placer-
Plumas-
Riverside-
Sacramento4
San Benito-
San Bernardino-
San Diego1
San Francisco-
San Joaquin-
San Luis Obispo-
San Mateo1
Santa Barbara-
Santa Clara-
Santa Cruz-
Shasta-
Sierra-
Siskiyou-
Solano-
Sonoma-
Stanislaus-
Sutter-
Tehama-
Trinity-
Tulare-
Tuolumne-
Ventura-
Yolo-
Yuba-
Total8

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

Press Releases

CDPH REPORTS FIRST CONFIRMED HUMAN WEST NILE VIRUS FATALITIES OF 2009

Sep 17, 2009

SACRAMENTO - A Fresno County man and a Merced County man are the first reported West Nile virus (WNV) fatalities in California this year, reported Dr. Gilberto Chavez, acting chief deputy director of the California Department of Public Health (CDPH).

"These fatalities underscore the importance of taking precautions to protect from mosquito bites," Chavez said. "Californians should use insect repellent and eliminate all sources of standing water that can sustain mosquito breeding."

WNV is transmitted to humans and animals through a mosquito bite. Mosquitoes become infected when they feed on infected birds. Despite these two fatalities, the number of reported WNV illnesses in California this year is lower than last year. In September 2008, there were 193 human cases. To date this year, 36 people in 10 California counties have been diagnosed with WNV.

"We generally expect the level of WNV activity to cycle from year to year and from region to region, but probably the greatest reason for the decreased activity in 2009 is the relatively cool summer compared to previous years," Chavez explained. "We can also credit better mosquito control efforts."

Most infected individuals will not experience any illness. Individuals 50 and older have a higher chance of getting sick and are more likely to develop serious symptoms when infected with WNV. People who have diabetes and/or hypertension are at greatest risk for serious illness.

Chavez said that the most effective ways for individuals to prevent exposure to mosquito bites and WNV are to remember the "Four D's":


  1. DEET - ApplyinspectrepellentcontainingDEET,picaradin,oiloflemon eucalyptus or IR 3535 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. DRESS - Wear clothing that reduces the risk of skin exposure.

  3. DAWN AND DUSK?Mosquitoes that carry WNV bite the early morning and evening so it is important to wear repellent at this time. Make sure that your doors and windows have tight-fitting screens to keep out mosquitoes. Repair or replace screens with tears or holes.

  4. 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 have a pond, use mosquito fish (available from your local mosquito and vector control agency) or commercially available products to eliminate mosquito larvae.


WestNile.ca.gov includes the latest information on WNV activity in the state. Report all dead birds and dead tree squirrels on the Web site or by calling toll-free 1-877-WNV- BIRD (968-2473).

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

As of May 26, 2017201720165Y AVG
Counties91110
Human cases100
Dead birds85331
Mosquito samples122720
Sentinel chickens000
YTD - Year to date corresponds to the same time last year or last five years.

- view all 2016 YTD activity -

WNV Reports

Weekly Report

05.26 Arbovirus Bulletin #8
05.26 2017 YTD WNV Activity Map
05.19 Arbovirus Bulletin #7

Humans

02.08 2016 Human WNV Incidence Report
02.08 2003-2016 WNV Case Summary
03.21 2015 Human WNV Incidence Report

Dead Birds

05.26Positive Counts by City/County for 2017
05.26Positive Species for 2017
05.26Reported, Tested, Positive 2017

Mosquitoes

05.26 AMOR - EVS Week 20
05.26 AMOR - GRAVID Week 20
05.26 AMOR - NJLT Week 20
- view report archives -