The West Nile Virus (WNV) is a mosquito-borne virus that can cause swelling and inflammation of the brain and spinal cord in horses, birds and humans. The virus is named after the West Nile region of Uganda, where the virus first appeared in 1937. Since the discovery of WNV, it has become widespread in Africa and Eurasia. WNV was identified in the New York area in 1999, and has since become established across the North American continent. It was first detected in Alberta in July 2003, in a wild bird. WNV is related to the viruses that cause St. Louis encephalitis and Japanese encephalitis.