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

Case Counts by County

CountyDead birds
Alameda1
Alpine-
Amador-
Butte4
Calaveras-
Colusa1
Contra Costa10
Del Norte-
El Dorado1
Fresno5
Glenn2
Humboldt1
Imperial-
Inyo-
Kern3
Kings1
Lake3
Lassen-
Los Angeles59
Madera1
Marin-
Mariposa-
Mendocino-
Merced1
Modoc-
Mono-
Monterey1
Napa-
Nevada1
Orange37
Placer2
Plumas-
Riverside29
Sacramento65
San Benito-
San Bernardino37
San Diego22
San Francisco1
San Joaquin6
San Luis Obispo-
San Mateo1
Santa Barbara-
Santa Clara7
Santa Cruz1
Shasta2
Sierra-
Siskiyou-
Solano2
Sonoma2
Stanislaus4
Sutter2
Tehama-
Trinity-
Tulare8
Tuolumne-
Ventura1
Yolo6
Yuba6
Total336

WNV Activity by County
Printable Version
2017 | 2016 | 2015 | 2014
2013 | 2012 | 2011
2010 | 2009 | 2008
2007

Press Releases

CDPH Confirms First Human West Nile Virus Death of 2016

Aug 5, 2016

SACRAMENTO - California Department of Public Health (CDPH) Director and State Health Officer Dr. Karen Smith today announced the first confirmed death in California due to West Nile virus (WNV). The deceased person was a senior citizen in Sacramento County.

"West Nile virus can cause a deadly infection in humans, and the elderly are particularly susceptible, as this unfortunate fatality illustrates," said Dr. Smith. "West Nile virus activity in the state is increasing, so I urge Californians to take every possible precaution to protect themselves against mosquito bites."

CDPH has reported ten human cases of WNV from eight California counties this year. In addition, 764 dead birds from 26 counties have tested positive for WNV in 2016 and 1,487 mosquito samples from 30 counties have also tested positive for WNV this year.

The number of WNV positive dead birds and mosquito samples exceeds the numbers at this same time last year and are above the state's most recent five-year average.

West Nile virus is influenced by many factors, including climate, the number and types of birds and mosquitoes in an area and the level of WNV immunity in birds. West Nile 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 serious neurologic illnesses such as encephalitis or meningitis.

People 50 years of age and older and individuals with diabetes or hypertension have a higher chance of getting sick and are more likely to develop complications.

CDPH recommends that individuals protect against mosquito bites and WNV 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. Insect repellents should not be used on children under two months of age.

  2. DAWN AND DUSK - Mosquitoes usually 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 out mosquitoes. Repair or replace screens that have tears or holes.

  3. DRAIN - Mosquitoes lay their eggs on standing water. Eliminate all sources of standing water on your property, by emptying flower pots, old car tires, buckets, and other containers. 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 WNV activity in the state. Californians are encouraged to report dead birds on the website 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 Sep 15, 2017201720165Y AVG
Counties423638
Human cases143199183
Dead birds33612381262
Mosquito samples297931902633
Sentinel chickens204280301
YTD - Year to date corresponds to the same time last year or last five years.

- view all 2016 YTD activity -

WNV Reports

Weekly Report

09.19 2017 US Arboviral Activity Update
09.18 2017 YTD WNV Activity Map
09.15 Arbovirus Bulletin #24

Humans

09.13 2017 Human WNV Incidence Report
09.13 2003-2017 WNV Case Summary
02.08 2016 Human WNV Incidence Report

Dead Birds

09.18Positive Counts by City/County for 2017
09.18Positive Species for 2017
09.18Reported, Tested, Positive 2017

Mosquitoes

09.15 AMOR - EVS Week 36
09.15 AMOR - GRAVID Week 36
09.15 AMOR - NJLT Week 36
- view report archives -