Sep. 21--Mosquito control officials are not ready to declare victory over West Nile virus after two California men died from the mosquito-borne disease, despite the low number of human infections this year.
On Sunday, Yolo County officials confirmed the first two human cases of West Nile virus this year -- a senior and a youth, 10 to 18 years old, both from Davis. Both are recovering.
The California Public Health Department announced last week the state's first two fatalities caused by the virus this year -- one in Merced County and the other in Fresno County. State officials urge people to continue to take precautions, though human cases traditionally diminish in fall as cooler temperatures arrive and mosquito populations recede.
Although the numbers of cases are down this year, that "doesn't decrease the potential seriousness of this disease," Dr. Joseph Iser, Yolo County health officer and director, said in a news release.
People typically develop symptoms between three and 14 days after they are bitten by an infected mosquito. About 80 percent of people who are infected with West Nile virus will not show any symptoms at all
Reports of human illnesses caused by West Nile are sharply down in California -- 36 this year, compared with 445 in 2008. Nationally, virus-linked sicknesses have totaled 280 this year, with eight deaths, compared with 1,356 illnesses and 44 deaths a year ago, the national Centers for Disease Control and Prevention reported.
The cooler summer and better reporting of mosquito breeding areas have combined to bring down this year's number, according to the CDC and other pest control agencies.
West Nile virus is transmitted to humans, birds, horses, and other animals by infected mosquitoes. Mosquitoes get the disease from infected birds while taking blood and can later pass it on when they bite animals or humans.
The virus was first isolated in the West Nile district of a northern province in Uganda in 1937. It was first detected in the United States in New York City in 1999. From there, the virus spread westward, arriving in California in 2003. West Nile virus is now the most prevalent mosquito-borne disease in the United States.
Roughly 20 percent of infected individuals develop West Nile fever. Symptoms often mimic typical flu symptoms, including fever, headache, fatigue, occasional skin rash and eye pain or swollen lymph glands.
The symptoms may last two to three weeks with an uneventful recovery, or the disease may progress to a severe case in roughly 1 percent of individuals.
Severe symptoms may include fever, seizures, weakness, change in mental status, paralysis and death, according to the Sacramento-Yolo Mosquito Control District.
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