Introduction of the West Nile Virus to North America Essay

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Introduction of the West Nile Virus to North America

A West Nile (WN) virus was first isolated in 1937 from the peripheral blood of a woman in the West Nile province of Uganda in Central Africa. Since then, WN viruses have been reported from North Africa (Egypt, Israel), East, Central, and South Africa, Asia (India, Pakistan), Borneo, Europe (Cyprus, France, Romania) and, most recently, the northeastern USA. Tests for antibody to WN suggest it has also been present in Thailand, the Philippines, Malaysia, Turkey, and Albania.
West Nile viruses are members of the virus family Flaviviridae and are closely related to Japanese encephalitis viruses from the Old World and St. Louis encephalitis (SLE) viruses from the New World. In addition,
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In 1952, 1953, and 1954, cases were reported from both areas, indicting the ability of this virus to be extremely focal in its epidemic transmission patterns.
Epidemics of WN occurred in the Rhone delta region of France in 1962, 1963, and 1964. The largest epidemic of WN, involving thousands of clinical cases, was reported in South Africa in 1974. Epidemic activity was again reported in South Africa in 1983 and 1984. Human cases were reported in southeast Romania in 1996 and 1997. Most recently, WN virus(es) was apparently introduced into the northeastern region of the borough of Queens in NYC during the summer of 1999.
West Nile is more mobile than other closely related viruses like the SLE viruses in North America and MVE viruses in Australia. West Nile viruses have spread from Africa to Western Europe, the Middle East, Eastern Europe, and now North America. To date, close relatives of WN like SLE and MVE have remained confined to their home regions.
THE DISEASE
In humans, infection with WN can cause clinical or subclincal symptoms. Clinical symptoms vary from temporary fever to serious encephalitis. The disease can be severe in the elderly, but is usually mild in healthy adults and children. The incubation period for WN is 3-6 days. Onset of disease symptoms is usually sudden, beginning with a sustained, elevated fever. Clinical infection can include severe headache; a rash, usually on the trunk; and swollen lymph nodes. Symptoms of WN infection can also include

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