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
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2007

Press Releases

West Nile Virus Activity Increases Throughout California

Jul 8, 2015


CONTACT: Anita Gore
Orville Thomas
(916) 440-7259

FOR IMMEDIATE RELEASE                                
PH15-048

SACRAMENTO - California Department of Public Health (CDPH) Director and State Health Officer Dr. Karen Smith today announced that the level of West Nile virus (WNV) activity is on the rise throughout the state.

"While there have been no human cases of West Nile virus reported so far this year, it is only a matter of time before we see the first case," Dr. Smith said. "As people go outdoors to enjoy the warm weather we've been experiencing, we'd like them to be safe and know how to protect themselves against West Nile virus."

Thirty-one California counties have reported WNV activity so far this year, 10 more than this time last year and above the five-year average of 18. To date, 240 mosquito samples have tested positive for WNV, six more than last year at this time.

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 West Nile virus 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.
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, and buckets. If you know of a swimming pool that is not being properly maintained, please contact your local mosquito and vector control agency.

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.

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).

Having problems with mosquitoes?

Locate your local mosquito and vector control agency
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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 -