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

Case Counts by County

CountyDead birds
Alameda10
Alpine-
Amador-
Butte1
Calaveras-
Colusa-
Contra Costa3
Del Norte-
El Dorado2
Fresno-
Glenn-
Humboldt1
Imperial-
Inyo-
Kern-
Kings-
Lake-
Lassen-
Los Angeles4
Madera-
Marin-
Mariposa-
Mendocino-
Merced-
Modoc-
Mono-
Monterey-
Napa-
Nevada-
Orange1
Placer19
Plumas-
Riverside3
Sacramento181
San Benito-
San Bernardino-
San Diego-
San Francisco-
San Joaquin7
San Luis Obispo-
San Mateo2
Santa Barbara-
Santa Clara26
Santa Cruz2
Shasta-
Sierra-
Siskiyou-
Solano-
Sonoma-
Stanislaus1
Sutter3
Tehama-
Trinity-
Tulare-
Tuolumne-
Ventura-
Yolo19
Yuba-
Total285

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 Aug 10, 2018201820175Y AVG
Counties333136
Human cases192232
Dead birds285172657
Mosquito samples94218051679
Sentinel chickens3858113
YTD - Year to date corresponds to the same time last year or last five years.

- view all 2018 YTD activity -

WNV Reports

Weekly Report

08.13 2018 YTD SLEV Activity Map
08.13 2018 YTD WNV Activity Map
08.10 Arbovirus Bulletin #19

Humans

08.09 2018 Human WNV Incidence Report
08.09 2003-2018 WNV Case Summary
03.29 2017 Human WNV Incidence Report

Dead Birds

08.10Reported, Tested, Positive 2018
08.10Positive Species for 2018
08.10Positive Counts by City/County for 2018

Mosquitoes

08.10 AMOR - EVS Week 31
08.10 AMOR - GRAVID Week 31
08.10 AMOR - NJLT Week 31
- view report archives -