CA West Nile Virus Website - 2004 Summary of WNV Activity

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4/5/05

West Nile virus activity was detected in all California counties in 2004 .

Humans

There were 830 human infections of WNV from 23 counties detected in California in 2004.
Sixty-six of these cases were first detected in asymptomatic individuals through screening done at blood banks - 15 later became symptomatic.
Of the 779 WNV cases with symptoms, 395 are classified as West Nile fever cases, 289 are classified as West Nile neuroinvasive disease, and 95 are of unknown status.
There have been 28 West Nile virus-related fatalities to date in California, in Glenn, Kern, Los Angeles, Orange, Riverside, San Bernardino, and Tehama counties.

Equines (Horses)

According to the California Department of Food and Agriculture, there have been 540 horse infections from 32 counties in 2004.
Of these West Nile virus infected horses, 228 have been euthanized or died.

Dead Birds

3,232 dead birds tested positive for WNV in California in 2004.
West Nile virus infected dead birds have been found in every county in California.
The top 4 species affected by WNV are 1) American Crows 2) Western Scrub-Jays 3) Yellow-billed Magpies and 4) Steller's Jays

Mosquito Pools and Sentinel Chickens

1,136 mosquito pools from 18 counties tested positive for WNV in 2004.
A mosquito pool is a collection of approximately 50 mosquitoes that are tested together for West Nile virus.
809 chickens from 22 counties tested positive for WNV antibodies (seroconverted) in 2004.

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