A mosquito-borne viral infection that is normally harmless to healthy people who, if infected, develop a mild INFLUENZA-like illness. However, the elderly and those in poor health, particularly immunocompromised patients, may develop fatal inflammation of the brain and spinal cord. In New York in 1999, more than 60 people were infected, of whom six died, while in Israel in 2000, 12 people died and more than 155 survived an outbreak. The disease is ENDEMIC in the Middle East and Africa, but has recently spread to parts of Europe, central Asia and Oceania; it is widespread in the US, with 1,267 notified cases in 2013. Mosquitoes bearing the flaviviridae-family virus usually contract it by biting infected poultry, but the infection has been found in mammals, such as cats, dogs and horses.