Three days after West Nile virus was confirmed in Nevada, county health officers at both ends of the state reported possible human cases of the mosquito-borne disease.
A possible case in southern Nevada's Clark County appears to be the first of someone contracting the disease in state, officials said Thursday.
Clark County Health District spokesman David Tonelli said preliminary tests showed the patient, described only as younger than 50, had the disease, including symptoms of meningitis.
Results of a more specific test to confirm the disease are pending, he said.
Tonelli said the affected person had recently traveled to a wilderness area in neighboring Nye County.
"They haven't identified an exact exposure point yet," Tonelli said. "It does look to be Nevada acquired."
In the Reno-area case, Washoe County health officials said it's impossible to tell where the person got the disease because they traveled extensively in recent weeks - to California, Louisiana and other Western states.
"Last year we had two cases that were imported from Colorado," said Dr. Mark Riddle of the Washoe District Health Department. "But last year we didn't have evidence of West Nile virus in Nevada.
"Now that we have evidence, we can't say for certain where the person contracted it," he said.
The Reno patient, also younger than 50, became ill earlier this month, was hospitalized with meningitis and has since fully recovered, Riddle said.
Preliminary tests conducted in Nevada and California indicate the illness was associated with West Nile virus, which affects the central nervous system and is transmitted by infected mosquitos. Results of a more specific test to confirm the disease are pending, Riddle said.
Meningitis is an inflammation of the spinal cord covering. Symptoms include severe headache, neck stiffness, back pain, numbness and high fever, Riddle said.
"There's a lot of cases of meningitis, and it's caused by a number of things," Riddle said. "This is the first probable case that we're pretty darn sure is associated with West Nile."
The disease first appeared in the United States in 1999 and has killed more than 560 people over the past five years. The disease has sickened more than 180 people across the country so far this year, according to the federal Centers for Disease Control and Prevention.
Although fatal in birds, symptoms of the disease are usually so mild to people that they are believed to go unnoticed in 80 percent of cases, federal health officials said. Fewer than one in five cases develop into mild flu-like symptoms, and less than 1 percent of cases can be fatal.
State veterinarian Dr. David Thain said his office is investigating "several" suspected equine cases of West Nile and awaiting test results.
State officials last year began urging horse owners to vaccinate their animals, which otherwise have about a 30 percent fatality rate.
There is no vaccine for people.
Nevada had escaped West Nile until this week when its presence was confirmed by tests conducted on a dead crow found in Carson City and mosquitos captured in the Lyon County communities of Silver Springs and Fernley.
Local and state officials have stepped up mosquito control and trapping, and increased bird surveillance to monitor the disease. Residents have been urged to report dead birds.
Riddle, who said his office has been inundated with calls, said health officials are mainly interested in dead crows or blue jays that have been dead for less than 24 hours.
"Those are the species that are most sensitive to West Nile and the best indicators of the disease," he said.
Health officials also reminded people to take preventive measures to avoid being bitten by mosquitos. That includes use of insect repellent, wearing long sleeves and pants, making sure house screens fit properly and draining any standing water around homes where mosquitos might breed.
On the Net:
Washoe District Health Department: www.co.washoe.nv.us/health
Nevada Department of Agriculture: www.agri.state.nv.us
National Centers for Disease Control and Prevention: www.cdc.gov