Case Counts by County

CountyDead birds
Alameda19
Alpine-
Amador-
Butte38
Calaveras-
Colusa3
Contra Costa11
Del Norte-
El Dorado4
Fresno3
Glenn4
Humboldt2
Imperial-
Inyo-
Kern1
Kings3
Lake5
Lassen-
Los Angeles103
Madera1
Marin3
Mariposa-
Mendocino-
Merced3
Modoc-
Mono-
Monterey-
Napa7
Nevada10
Orange83
Placer21
Plumas-
Riverside82
Sacramento103
San Benito-
San Bernardino25
San Diego355
San Francisco-
San Joaquin18
San Luis Obispo-
San Mateo23
Santa Barbara3
Santa Clara231
Santa Cruz-
Shasta16
Sierra-
Siskiyou-
Solano10
Sonoma11
Stanislaus14
Sutter16
Tehama-
Trinity2
Tulare23
Tuolumne-
Ventura26
Yolo61
Yuba6
Total1349

WNV Activity by County
Printable Version
2015 | 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 Dec 30, 2015201520145Y AVG
Counties414032
Human cases737801362
Dead birds134924421205
Mosquito samples332933402161
Sentinel chickens449443372
YTD - Year to date corresponds to the same time last year or last five years.

- view all 2014 YTD activity -

WNV Reports

Weekly Report

01.12 2015 US Arboviral Activity Update
01.12 2015 YTD WNV Activity Map
12.18 Arbovirus Bulletin #41

Humans

01.06 2015 Human WNV Incidence Report
01.06 2003-2015 WNV Case Summary
03.09 2014 Human WNV Incidence Report

Dead Birds

01.12Positive Species for 2015
01.12Positive Counts by City/County for 2015
01.12Reported, Tested, Positive 2015

Mosquitoes

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