Nevada appears to have been spared an onslaught of West Nile virus this year and remains one of only four states in the contiguous United States yet to report any cases.
"We missed that bullet," State Veterinarian David Thain said Tuesday.
While isolated cases could still turn up in September or early October, Thain said the chances are lessening as summer turns to fall.
"It's cooling off in the nights enough that mosquitoes are kind of disappearing in numbers," he said. "I think if we do get some cases, it'll be a very small number.
"I'm surprised we haven't had it, but that's just the fickle finger of Mother Nature and the way diseases spread," he said.
Thain said Nevada's expansive desert may have shielded the state from the disease.
"It's a pretty good stretch of desert," he said. "I think that's probably what's acting as a buffer for us. We don't have a lot of cross movement with animals and birds because of the way the Great Basin is laid out."
The Washoe District Health Department plans to treat Reno-area wetlands one more time for mosquitoes on Thursday. The aerial treatments began in May when the potential of the mosquito borne illness making its way to Nevada seemed likely.
West Nile first appeared in the United States in New York in 1999. Since then, it has advanced rapidly across the country. Only Nevada, Oregon, Washington and Idaho have yet to report any cases, according to the National Centers for Disease Control and Prevention.
Mosquitoes pick up the disease from infected birds and transmit it to the people and horses they bite. The virus causes fevers and aches and can lead to potentially fatal swelling of the brain.
Horses vaccinated against the disease will need annual booster shots to retain protection against infection, Thain said.
There is no vaccination for people
So far this year, 3,541 people have been infected with the virus and 66 have died, according to the CDC's Web site. Last year, 4,156 people were infected and 284 died in the largest West Nile outbreak in the Western Hemisphere.
Thain said the Nevada Department of Agriculture will continue testing mosquitoes caught in traps and blood samples drawn from wild horses and sentinel flocks for signs of the disease through early October.
Additionally, people still are being asked to watch for sick or dead birds - specifically ravens, crows, magpies and jays.
"If anyone sees any of those birds that seem ill or just died, we'd like to know about it for West Nile testing," Thain said.
Thain said while Nevada may have escaped the virus this year, it is not immune.
"In all likelihood it'll hit us next year," he said.
On the Net:
Centers for Disease Control and Prevention: http://www.cdc.gov
Nevada Department of Agriculture: http://www.agri.state.nv.us
kolotv.com Extended Web Coverage
West Nile virus Facts
How is the West Nile virus Spread?
Symptoms of the Virus
Source: www.vdh.state.va.us contributed to this report