California's human West Nile tally hit 500 cases Friday, up 20 percent since Tuesday. Among them were 15 newly reported cases in Sacramento County, nine cases in Placer County and four in Yolo County.
No West Nile deaths have been logged in California since Aug. 26, when reports of the deaths of a Sacramento County man and a Fresno County woman brought the state's death toll to eight.
Still, health officials say they can't predict if the numbers of cases in California will continue to climb or begin to drop for the season.
The first week of September in 2004 marked the peak of human West Nile infection last year, with the vast majority of cases reported in Southern California. By year's end, the state had tallied 830 cases.
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So far this year, West Nile cases have followed almost the same pattern 2004, starting in June, and rising sharply through July and August.
This year, however, most West Nile infections are in Northern and Central California. Sacramento County continues to lead the count, with 112 cases as of Friday.
Other California hot spots are Kern, Stanislaus, Tulare, Fresno and Riverside counties. Last year's epicenter for West Nile, San Bernardino County with 197 cases, has had a mild year with just 15 cases.
West Nile is spread by the bite of an infected mosquito and cannot be transmitted from one person to another. About 80 percent of those infected will show no symptoms.
Less than 1 percent of those infected with the virus will require hospitalization for symptoms of encephalitis, meningitis and poliolike syndrome. The elderly and people with compromised immune systems are most at risk for the most serious consequences of the disease.
Most of those who do get sick will experience a fever, headache, muscle and joint soreness and rash. There is no known treatment for West Nile virus.
"This isn't always a benign illness," said Carol Glaser, chief of the viral disease laboratory at the state Department of Health Services. "An important portion of patients can get sicker. Not everybody gets better in a week."
Ground spraying update
The Placer Mosquito Abatement District sprayed by truck Friday in Roseville and was to have continued overnight in south Roseville. The district said it plans to spray the Sun City Roseville subdivision Wednesday. Weather permitting, the spraying will occur from 1 to 4 a.m. The areas that were to have been sprayed early this morning are along roads bounded by Washington Boulevard, Pleasant Grove Boulevard, Foothills Boulevard, Cirby Way and Vernon Street.
Roseville and South Placer County residents who want to be placed on Placer Mosquito Abatement District's "no spray" list should notify the district by e-mail at firstname.lastname@example.org, or by calling (916) 435-2140 and providing their name, telephone number and address.
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- The Bee's Dorsey Griffith can be reached at (916) 321-1089 or email@example.com.