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Maps and Data  > 2007 WNV Activity by County Oct. 7, 2008 2:50PM

West Nile virus has been detected in 45/ 58 California Counties in 2007.

2007 WNV Activity by County

Total Positive Counties: 45

CountyHuman CasesHorsesDead BirdsMosquito SamplesSentinel ChickensSquirrels
State Totals309232232180542125
Alameda1-81-1
Alpine------
Amador--3---
Butte5-36526-
Calaveras1-1---
Colusa1-3-1-
Contra Costa427825146
Del Norte------
El Dorado1-5---
Fresno11315113-
Glenn--1713-
Humboldt--1---
Imperial---721-
Inyo------
Kern--10710-
Kings1-1---
Lake-123--
Lassen---1--
Los Angeles102-402457879
Madera--21--
Marin--1---
Mariposa------
Mendocino--1---
Merced1-5---
Modoc--1---
Mono--2---
Monterey--5---
Napa------
Nevada--5---
Orange60258927634
Placer413279-
Plumas------
Riverside4953911493-
Sacramento10212027761
San Benito------
San Bernardino141162151514
San Diego2144693713-
San Francisco------
San Joaquin10-6919413-
San Luis Obispo------
San Mateo--2---
Santa Barbara--1---
Santa Clara1-111--
Santa Cruz--3---
Shasta1-7---
Sierra------
Siskiyou------
Solano1-71--
Sonoma--61--
Stanislaus162457530-
Sutter--2118-
Tehama1-6---
Trinity------
Tulare21486215-
Tuolumne------
Ventura--17-4-
Yolo11618--
Yuba---11-
State Totals309232232180542125


* A mosquito sample, or "pool," is a collection of approximately 50 mosquitoes that are tested together for West Nile virus.

** WNV and SLE (St. Louis encephalitis) are closely related viruses in the family Flaviviridae and preliminary testing cannot distinguish between these two viruses.  Further testing is conducted as needed to determine if the sentinel chickens are antibody positive to WNV or SLE.

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