Nevada remains free of West Nile virus, a seasonal infection transmitted by mosquitoes.
"We've seen no human, avian, animal or mosquito infections in Nevada," said Martha Framsted, spokeswoman for the Nevada State Health Division. "We're continuing to watch it very carefully. We won't be surprised to see a case, but we're keeping our fingers crossed.
"We've found cases in eastern Utah, but nothing in Idaho, Oregon or Washington," she said.
Dr. David Thain of the Nevada Department of Agriculture said sentinel flocks of chickens are tested every two weeks throughout Northern Nevada, including Carson City, Washoe, Lyon, White Pine, Elko, Lander, Humbolt and Churchill counties.
"I wouldn't be surprised to see West Nile show up any time," Thain said. "My guess is in September or October."
Dead birds are being tested and veterinarians are submitting blood samples from any horses with symptoms that fit the clinical picture for West Nile. The Department of Agriculture is also testing any wild horses gathered from the range.
Mosquitos are gathered and tested from throughout the state. In Washoe County, the Canada goose population, which is gathered once a year for reintroduction into the wild, is also being tested, said Director Scott Munson, director of the Washoe County Health Department.
West Nile cases in humans grew from an initial outbreak of 62 in 1999 to 4,156 reported cases, including 284 deaths in 2002. This year, 772 human cases have been reported to the Centers for Disease Control and Prevention in Atlanta.
Human illness from West Nile virus is rare, even in areas where the virus has been reported and most people infected with the virus will have either no symptoms, or mild ones.
About one in five people will develop fever, headache, and body aches, occasionally with a skin rash on the trunk of the body and swollen lymph glands.
One in 150 will develop encephalitis or meningitis, characterized by a number of symptoms including headache, high fever, neck stiffness, coma, muscle weakness and paralysis.
The virus is transmitted primarily between mosquitos and bird hosts. The birds sustaining the virus in the bloodstream for one to four days, spreading the virus to other mosquitoes during that period.