Case Counts by County

CountyDead birds
Alameda96
Alpine-
Amador-
Butte22
Calaveras-
Colusa4
Contra Costa44
Del Norte-
El Dorado7
Fresno9
Glenn4
Humboldt2
Imperial-
Inyo-
Kern3
Kings3
Lake18
Lassen-
Los Angeles99
Madera5
Marin6
Mariposa-
Mendocino-
Merced8
Modoc-
Mono-
Monterey-
Napa12
Nevada-
Orange426
Placer40
Plumas-
Riverside1
Sacramento294
San Benito-
San Bernardino17
San Diego30
San Francisco-
San Joaquin53
San Luis Obispo-
San Mateo19
Santa Barbara2
Santa Clara921
Santa Cruz1
Shasta6
Sierra-
Siskiyou-
Solano33
Sonoma37
Stanislaus47
Sutter19
Tehama-
Trinity-
Tulare40
Tuolumne-
Ventura7
Yolo71
Yuba16
Total2422

WNV Activity by County
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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 previous year and previous five-year average to date

As of Nov 19, 2014201420135Y AVG
Counties404440
Human cases752356226
Dead birds24221246897
Mosquito samples333825201961
Sentinel chickens437481424
YTD - Year to date corresponds to the same time last year or last five years.

- view all 2013 YTD activity -

WNV Reports

Weekly Report

11.19 2014 YTD WNV Activity Map
11.18 2014 US Arboviral Activity Update
11.14 Arbovirus Bulletin #39

Humans

11.17 2014 Human WNV Incidence Report
11.17 2003-2014 WNV Case Summary
08.12 2013 Human WNV Incidence Report

Dead Birds

11.19Reported, Tested, Positive 2014
11.19Positive Counts by City/County for 2014
11.19Positive Species for 2014

Mosquitoes

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