West Nile Virus was detected in mosquito pool samples from Lyon, Churchill and Humboldt counties this week. One bird in Churchill County tested positive and one case has been confirmed in a horse this season, according to a report by the Nevada Department of Agriculture.
All tests in Douglas County have been negative so far, according to Ron Lynch, manager of Douglas County's Mosquito Abatement District.
"I've turned in samples from two dead owls, but both were negative," he said. "The first pool of mosquitoes from Glenbrook came back negative, as were the mosquito pools from the Valley and at Topaz."
Lynch said he's been spraying for mosquitoes since April, in neighborhoods from Indian Hills and Johnson Lane to Topaz Ranch Estates. A majority of the fogging is done by hand.
"The plane is used in places like Mottsville Lane, where we don't have to worry about houses and people," he said. "Anymore, it's hard to get around the houses with the plane."
A seasonal epidemic that flares up in the summer and continues into the fall, West Nile Virus is spread by mosquitoes, which acquire the virus when they feed on infected birds, according to the Centers for Disease Control and Prevention in Atlanta, Ga.
Martha Framsted, spokesman for the Nevada State Health Division, said prevention is the key.
It's important to wear insect repellent when outdoors, especially at dusk and dawn when mosquitoes are most active. Long sleeves and pants are recommended and people should remove any standing water around their homes that could provide breeding grounds for mosquitoes.
"We've had a very wet winter and we don't know what this season will bring," she said.
Serious symptoms, including a potentially fatal encephalitis, will occur in about one in 150 people infected with West Nile, but the infection is so mild in 80 percent of the people contracting it that there are no symptoms.
About 20 percent will experience flu-like symptoms, including fever, headache, body aches, nausea, vomiting and sometimes swollen lymph glands or rash, according to the Centers for Disease Control and Prevention.
Mosquito samples are tested for other viruses, including St. Louis Encephalitis and Western Equine Encephalitis. The later was reported this week in a sample from White Pine County.
The disease affects horses and humans, but most people infected with this disease will have either no symptoms or a very mild illness. Most of the severe human cases begin with a sudden onset of fever, headache, stiff neck, vomiting and fatigue.
There is no treatment for this type of encephalitis other than supportive care until the acute or severe phase of the illness is over, according to information from the Department of Agriculture.
Since it was first detected in New York in 1999, West Nile Virus spread from the northeastern U.S. to the south central states and westward. It was first detected in Nevada in 2004 and since that time, has been reported throughout the state.
In 2005, West Nile activity began in late June and ended in mid-September. A total of positive mosquito pools were reported around the state, the areas of highest concentration in Washoe,(26) Lyon,(25), Clark,(25) and Churchill (22) counties. Nye County had a total of 17 and the numbers drop significantly from there. Lincoln County had 13 and Douglas County, six.
Thirty human cases of West Nile Virus were confirmed in Nevada from July to October 2005, but no deaths were reported, according to Framsted.
Susie Vasquez can be reached at svasquez@recordcourier.com or 782-5121, ext. 211.
