West Nile Virus (WNV) is a mosquito-borne virus which can cause West Nile encephalitis (inflammation of the brain). Although this virus is commonly found in Africa, West Asia and the Middle East, it is believed that the virus appeared in the eastern United States sometime in the summer of 1999. It is closely related to the St. Louis encephalitis virus commonly found in the southeastern and mid-western U.S., and only rarely in the northeast.
Prior to August of 1999, WNV had never been reported in the U.S. In 1999, 62 cases of the severe disease occurred in the New York City area, resulting in 7 deaths.
Because of this recent outbreak, public health and mosquito control professionals have heightened surveillance efforts to determine the most effective methods of mosquito control.