Where did West Nile virus come from?
West Nile virus is named after the West Nile district of Uganda where the virus was first isolated in 1937. Outbreaks of the West Nile illness have occurred in Egypt, Asia, Israel, South Africa, and parts of Europe and Australia. Before 1999, WNV had not been found in the United States. The virus may have been brought to the United States by an infected bird that was either imported or migrated 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. The virus has been reported in nearly all states. How is West Nile virus transmitted? Mosquitoes draw the virus from infected birds and transmit it to other animals, including humans, through bites. West Nile viral encephalitis develops when the virus multiplies and crosses the blood-brain barrier. West Nile virus is not transmitted directly from animal to person, person to animal, animal to animal or person to person; however, rare instances of transmission via organ transplantation, blood transfusion, transplacental infection, and breastfeeding have been reported. Cats have been infected experimentally by eating WNV-infected mice. Ticks infected with the virus have been
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 until 1999 had 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.
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 until 1999 had 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. U.S. Senator Patrick Leahy has now questioned if bioterrorism could be involved, but there is no corroborating evidence to date, although the virus was first discovered in the vicinity of the United Nations in New York City. How Many Cases of West Nile encephalitis in humans have occurred in the U.S.? In 1999 when West Nile was first diagnosed in the U.S., 62 cases of severe disease, including 7 deaths, occurred in the New York area. In 2000, 21 cases were reported, including 2 deaths in the New York City area. In 2001, there were 66 human cases of severe disease and 9 deaths. In 2002, the virus spread coast to coast, with cases from Florid
