Where did West Nile virus come from?
A. West Nile virus has been commonly found in humans and birds and other vertebrates in Africa, Eastern Europe, West Asia, and the Middle East, but has not previously been documented in the Western Hemisphere. It is not known from where the U.S. virus originated, but it is most closely related genetically to strains found in the Middle East.
Outbreaks of West Nile virus have occurred in Africa, Egypt, Israel, Asia, Romania, Russia and France. Before 1999, West Nile virus had never before been found in the Western Hemisphere. The virus was most likely introduced by an infected bird or mosquito that was imported from a country where the virus is common.
West Nile virus was first identified in the West Nile district of Uganda in 1937, and has since been found in other parts of Africa, Eastern Europe, West Asia, the Middle East, and the United States. The strain of virus found in the United States most closely resembles that found in the Mediterranean and Middle East.
West Nile virus has been commonly found in humans and birds and other vertebrates in Africa, Eastern Europe, West Asia, and the Middle East. West Nile virus was first isolated in the West Nile province of Uganda in 1937 (3,4). The first recorded large epidemics occurred in Israel during 1951-1954, and the largest recorded epidemic to date occurred in South Africa during 1974. Large human outbreaks of WN Encephalitis occurred in Israel in 2000 and have occurred in Southern France (1962), southeastern Romania (1996) and in south-central Russia (1999) (5,6). Until 1999, West Nile encephalitis had not been documented in the Western Hemisphere. It is not known where the U.S. WNV originated, but it is most closely related genetically to strains found in the Middle East.
West Nile virus has been commonly found in humans and birds and other vertebrates in Africa, Eastern Europe, West Asia, and the Middle East. West Nile virus was first isolated in the West Nile province of Uganda in 1937 (3,4). The first recorded large epidemics occurred in Israel during 1951-1954, and the largest recorded epidemic to date occurred in South Africa during 1974.
