The Nevada Department of Agriculture has confirmed a crow found dead near Yerington was carrying the West Nile virus.
The crow was turned over to the state by a worker at the Mason Valley Mosquito Abatement District.
"We have tested over 1,500 mosquito pools, 40 dead birds and 36 horse samples this season and it's our first positive for (West Nile virus)," said Dr. Anette Rink, supervisor of the department's Animal Disease and Food Safety Laboratory.
"The bottom line is the West Nile virus is in Nevada," said State Health Officer Bradford Lee. "Everyone needs to practice preventative measures."
He said that mans making sure screens fit properly, eliminating standing water that could be used by mosquitos to breed and using insect repellent when outside.
State Veterinarian David Thain also urged horse owners to have their animals vaccinated.
While the crow is the first confirmed bird death from West Nile virus, Rink said two mosquito pools have tested positive for St. Louis encephalitis.
Nevada's first case of the West Nile Virus was found in Carson City last July, detected in a dead bird.
Since then, however, the disease has rarely manifested itself in the city.
Only one of the state's 44 human cases was recorded here last year, while nearby Churchill County, with a population about half the size, racked up 15. Of 116 animals reported to have been infected, nearly all horses, six were in Carson City.
The virus causes mild flu-like symptoms in the vast majority of people it infects, but a small percentage of people develop more severe forms of illness that swell the brain and spinal column, sometimes leading to death.
In 2004, 2,470 human cases and 88 deaths were reported nationwide.
Horses, which can be inoculated against the virus. are far more susceptible to it. Of 130 horses confirmed to have West Nile virus last summer, 50 died.
St. Louis encephalitis can produce the same flu-like symptoms that are often found in the West Nile virus and both are spread through mosquito bites.
However, the encephalitis strain rarely shows up in horses. Birds and humans can contract St. Louis encephalitis.