California State Public Health Officer Announces Detection of West Nile Virus in Seven New Counties

SACRAMENTO -- Dead crows found in Alameda, Glenn, Humboldt, Marin, Placer, Solano, and Sonoma counties have tested positive for West Nile virus (WNV), marking the first evidence of the virus in those counties, Dr. Richard Joseph Jackson, state public health officer, announced today. WNV has now been detected in 28 counties statewide.

"As West Nile virus continues to spread across the state, it's important for all Californians to take steps now to protect themselves from mosquito bites," Jackson said.

Evidence of WNV in either dead birds or mosquitoes has previously been found in the counties of Butte, Contra Costa, Fresno, Imperial, Kern, Kings, Los Angeles, Mendocino, Orange, Riverside, Sacramento, San Diego, San Bernardino, San Joaquin, Santa Barbara, Santa Clara, Shasta, Stanislaus, Tehama, Tulare and Ventura.

To date, 85 Californians have tested positive for WNV and two have died. The deceased were elderly men, one from Orange and the other from San Bernardino counties. Four individuals were exposed to WNV thru blood transfusions and have not become ill.

The illnesses include 45 in San Bernardino County, 22 in Los Angeles County, 12 in Riverside County, two in Fresno and Orange counties, and one in Imperial and Kern counties.

Most individuals who are infected with WNV will not experience any illness. Approximately 10 percent to 15 percent of infected individuals will have only mild to moderate symptoms, such as fever, headache and body aches. Less than 1 percent of individuals will develop serious neurologic illness such as encephalitis and meningitis. The elderly and those with lowered immune systems are more susceptible to serious illness.

In recognition of the public health threat posed by WNV, the recently approved state budget includes $977,000 in state funds to boost efforts to monitor and control the spread of WNV. The funds would be used to expand surveillance activities to enhance detection of the virus and prompt control efforts.

WNV is transmitted to humans and animals through a mosquito bite. Mosquitoes become infected when they feed on infected birds.

For the year to date, WNV has been found in 1,229 dead birds, 341 "pools" of mosquitoes and 127 sentinel chickens.

The current surveillance program to monitor for WNV in California has been established by CDHS in collaboration with the University of California, Davis, California Department of Food and Agriculture, local mosquito and vector control districts, local health departments and other state and local agencies.

WNV has also infected 44 horses, 24 of which have died. Since horses are susceptible to WNV and a vaccine is available for horses, horse owners are advised to contact their veterinarians about timely vaccinations.

Source: California Department of Health Services