Case Counts by County

CountyDead birds
Alameda13
Alpine-
Amador-
Butte2
Calaveras-
Colusa1
Contra Costa19
Del Norte-
El Dorado1
Fresno7
Glenn1
Humboldt1
Imperial-
Inyo-
Kern2
Kings1
Lake5
Lassen-
Los Angeles9
Madera4
Marin2
Mariposa-
Mendocino-
Merced-
Modoc-
Mono-
Monterey-
Napa5
Nevada-
Orange55
Placer16
Plumas-
Riverside-
Sacramento143
San Benito-
San Bernardino2
San Diego1
San Francisco-
San Joaquin23
San Luis Obispo-
San Mateo3
Santa Barbara-
Santa Clara429
Santa Cruz1
Shasta2
Sierra-
Siskiyou-
Solano27
Sonoma8
Stanislaus17
Sutter13
Tehama-
Trinity-
Tulare32
Tuolumne-
Ventura1
Yolo21
Yuba5
Total872

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

Press Releases

EARLY ONSET OF WARM WEATHER TRIGGERS AN EARLY WEST NILE VIRUS SEASON

Apr 23, 2007

SACRAMENTO - Unusually high temperatures throughout the state in March triggered an earlier than normal start to the West Nile virus (WNV) season, State Public Health Officer Dr. Mark Horton warned today.

"Mosquitoes that carry West Nile virus are breeding earlier this year due to warm weather," Horton said. "While no predictions can be made about the severity of West Nile virus this season, Californians should begin taking precautions to protect themselves from mosquito bites by eliminating all sources of standing water that can support mosquito breeding and applying insect repellent containing DEET."

WNV was first detected in California five years ago. So far this year, no human cases of WNV have been identified. However, the virus has been detected in mosquito pools, sentinel chickens or horses in eight counties: Imperial, Los Angeles, Orange, Riverside, Santa Clara, San Diego, Sonoma and Stanislaus.

In 2006, a total of 292 human WNV infections, including seven deaths, were reported in the 54 counties that detected WNV activity. Of the 58 horses that also tested positive for WNV, 24 died or were euthanized. WNV is transmitted to humans and animals through a mosquito bite. Mosquitoes become infected when they feed on infected birds.

Governor Arnold Schwarzenegger has invested a total of $15 million over the last two years to enhance mosquito control efforts. This funding has supplemented the resources of existing mosquito control programs statewide and expanded efforts in areas of the state not covered to combat WNV. This investment in equipment and other products to control mosquitoes continues to benefit mosquito control efforts this year.

Horton reminded Californians of three simple ways to protect themselves from WNV:


  • DEET - Apply inspect repellent containing DEET, picaradin or oil of lemon eucalyptus 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.

  • DAWN AND DUSK - Mosquitoes that carry WNV bite in 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.

  • 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 or commercially available products to eliminate mosquito larvae.

California's WNV Web site - www.westnile.ca.gov - has been updated to make it easier for the public to find the latest information on WNV activity in the state. In addition to reporting all dead birds, Californians are encouraged to report dead tree squirrels, three types of which have tested positive for WNV in California: the Western Gray, Fox and Eastern Gray. The Web site also includes information on the most common birds found with WNV. Dead birds and squirrels can be reported on the Web site or by calling (877) 968-2473.

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Compared to 2013 YTD

As of Jul 25, 201420132014
Counties3335
Human cases415
Dead birds325872
Mosquito samples761980
Sentinel chickens7939
2013 YTD - Year to date corresponds to the same time last year.

- view all 2013 YTD activity -

WNV Reports

Weekly Report

07.25 Arbovirus Bulletin #23
07.25 2014 YTD WNV Activity Map
07.18 Arbovirus Bulletin #22

Humans

07.21 2014 Human WNV Incidence Report
07.21 2003-2014 WNV Case Summary
04.21 2013 Human WNV Incidence Report

Dead Birds

07.25Reported, Tested, Positive 2014
07.25Positive Counts by City/County for 2014
07.25Positive Species for 2014

Mosquitoes

07.25 AMOR - EVS Week 29
07.25 AMOR - GRAVID Week 29
07.25 AMOR - NJLT Week 29

Horses

12.16 2010 Equine WNV Result Map
12.16 2010 Confirmed Equine Cases Report
05.26 2009 Equine WNV Result Map
- view report archives -