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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2013 | 2012 | 2011
2010 | 2009 | 2008
2007

Press Releases

CDPH Reports Increased West Nile Virus Activity Statewide

Jul 22, 2016

SACRAMENTO - The California Department of Public Health (CDPH) is reporting increased West Nile virus activity across the state and is investigating numerous suspect cases in humans. While the first human case has not been confirmed by CDPH, a resident of Los Angeles County has symptoms consistent with West Nile virus disease. Initial tests on that patient indicate a probable West Nile virus diagnosis, which requires further testing for confirmation.

"Californians should take every possible precaution to avoid mosquito bites," said CDPH Director and State Public Health Officer Dr. Karen Smith. "Simple steps, like applying repellent, wearing long-sleeved shirts and pants in the early morning and evening, and draining standing water near your home can help to prevent bites from infected mosquitos."

To date in 2016, West Nile virus has been detected in mosquitoes and birds in 30 California counties. Approximately 600 dead birds and 896 mosquito pools sampled in California this year have been found to harbor the virus.

West Nile virus 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. Recent data also indicate that people with diabetes and/or hypertension are at greatest risk for serious illness.

CDPH recommends that individuals prevent exposure to mosquito bites and West Nile virus 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 mosquitoes from biting. 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 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 or drain all sources of standing water around homes and properties, including buckets, old car tires, rain gutters, birdbaths, and pet bowls. If a swimming pool is not being properly maintained, please contact the local mosquito and vector control agency.

California's West Nile virus website includes the latest information on West Nile virus activity in the state. Californians are encouraged to report all 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 22, 2017201720165Y AVG
Counties423739
Human cases174234226
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

09.22 2017 YTD WNV Activity Map
09.19 2017 US Arboviral Activity Update
09.15 Arbovirus Bulletin #24

Humans

09.20 2003-2017 WNV Case Summary
09.17 2017 Human WNV Incidence Report
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 -