The disease was originally confined to New York, but by early last fall the virus had been identified in North Carolina.
Birds are the natural host for the virus, which can be fatal to birds and humans.
WNV can infect humans, horses and wildlife. In people, it can cause West Nile encephalitis, a potentially deadly inflammation of the brain. However, some people who are infected may never know it, and others may only experience mild flu-like symptoms or headaches. It is estimated that as many as 2500 people were exposed to WNV in the 1999 New York outbreak but never developed any symptoms. That is because their immune systems generated antibodies rapidly enough to prevent the onset of symptoms.