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

Case Counts by County

CountyDead birds
Alameda2
Alpine-
Amador-
Butte5
Calaveras-
Colusa1
Contra Costa19
Del Norte-
El Dorado2
Fresno5
Glenn2
Humboldt1
Imperial-
Inyo-
Kern3
Kings1
Lake5
Lassen-
Los Angeles100
Madera1
Marin1
Mariposa-
Mendocino-
Merced1
Modoc-
Mono-
Monterey1
Napa-
Nevada1
Orange55
Placer4
Plumas-
Riverside41
Sacramento86
San Benito-
San Bernardino45
San Diego41
San Francisco1
San Joaquin7
San Luis Obispo6
San Mateo1
Santa Barbara1
Santa Clara12
Santa Cruz1
Shasta2
Sierra-
Siskiyou-
Solano4
Sonoma5
Stanislaus6
Sutter3
Tehama-
Trinity-
Tulare8
Tuolumne-
Ventura2
Yolo14
Yuba6
Total502

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

Press Releases

CDPH Confirms First Human West Nile Virus Death of 2015

Jul 20, 2015

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 Nevada County.

"This death is a tragic reminder of how severe West Nile virus disease can be," said Dr. Smith. "West Nile virus activity is more widespread in 2015 than in years past. Californians need to be vigilant in protecting themselves."

WNV is influenced by many factors such as climate, the number and types of birds and mosquitoes in an area, and the level of immunity in birds to WNV. It is possible that the drought has contributed to WNV amplification by reducing sources of water for birds and mosquitoes. As birds and mosquitoes seek water, they are coming into closer contact and amplifying the transmission of the virus.

Thirty-three California counties have reported WNV activity so far this year, four more than this time last year and above the five-year average of 22. To date, 497 mosquito samples have tested positive for WNV, which exceeds the five-year average of 330.

WNV 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 one 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. Studies also indicate that those with diabetes and/or hypertension are at greatest risk for serious illness.

CDPH recommends that individuals prevent exposure to 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. DEET can be used safely on infants and children two 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 out mosquitoes. 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, 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.

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

As of Nov 17, 2017201720165Y AVG
Counties473841
Human cases465395504
Dead birds50213461592
Mosquito samples336035063104
Sentinel chickens304343448
YTD - Year to date corresponds to the same time last year or last five years.

- view all 2016 YTD activity -

WNV Reports

Weekly Report

11.17 Arbovirus Bulletin #33
11.17 2017 YTD WNV Activity Map
11.14 2017 US Arboviral Activity Update

Humans

11.15 2017 Human WNV Incidence Report
11.15 2003-2017 WNV Case Summary
02.08 2016 Human WNV Incidence Report

Dead Birds

11.17Positive Counts by City/County for 2017
11.17Positive Species for 2017
11.17Reported, Tested, Positive 2017

Mosquitoes

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