West Nile virus is spreading in California, having infected 78 people so far this year, health officials said on Wednesday. A record number of 195 mosquito samples taken this week tested positive for the virus, compared to the previous
Pre-2008 weekly record high of 151 reported on July 22, 2005, according to California Department of Public Health statistics.
The test results serve as an indicator of how hard the virus is hitting the state, said Susanne Kluh, scientific and technical services director for the Greater Los Angeles County Vector Control District.
She warned that the height of West Nile virus season in California is near, saying that "the most activity we see is in August and September."
Cooler temperatures coming in the fall will hinder the virus` ability to multiply in infected mosquitoes, making it more difficult to spread to larger animals, she said.
Despite health experts` warnings that 2008 is shaping up to be a virulent year for West Nile, only 78 cases of the disease in humans have been reported statewide, compared to 120 by this time last year, and 168 by this time in 2004, which was considered to be the worst year for West Nile virus in Southern California.
Twenty-five of this year`s cases have been from Los Angeles County, compared to four by this time last year.
Kluh said she suspected that the low numbers of reported cases in humans had more to do with the virus going undetected in infected people.
"Human cases, as we see them, may not be the complete picture," she said. "They`re what public awareness allows us to see."
Roughly 80 percent of West Nile virus human infection cases show no symptoms of the disease, while about 20 percent show mild symptoms that may include fever, headache, body aches, nausea and vomiting -- things that are sometimes chalked up as a simple "summer fever," Kluh said.
About one out of more than every 150 infected people will develop severe illness, with symptoms such as convulsions, vision loss, numbness and paralysis. The symptoms can last for several weeks and have the potential to be fatal.
No human fatalities from the virus have been reported this year. Last year, 21 were reported statewide.
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