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COPYRIGHT 2004 Jannetti Publications, Inc.
In the summer of 1999, two strange seemingly unrelated events in New York City were reported in the news ("Anatomy of an Outbreak," 1999). In the hospital, aging patients with an unknown cause were confused, feverish, and weak to the point of paralysis. At the Bronx Zoo, crows were hobbling around shaky and disoriented and dying in record numbers. After several false starts, researchers were able to link the strange afflictions--both human and avian--to the West Nile virus (WNV).
Recognizing the importance of monitoring avian death rates, a surveillance system was quickly set up to track spread of West Nile virus in the eastern and southern United States. Surveillance showed expansion of the virus consistent with bird migration patterns. By the end of March 2004, WNV had spread to all but four states, with 45 states and the District of Columbia reporting human cases (see Figure 1). The 1999 initial U.S. outbreak of 62 disease cases grew to 9,389 reported cases in 2003, including 246 deaths (Centers for Disease Control [CDC], 2004).
Transmission
WNV is a flavivirus commonly found in Africa, Eastern Europe, West Asia, and the Middle East. The virus can infect humans, birds, mosquitoes, horses, and some other mammals. Since the original isolation of WNV in the West Nile district of Uganda in 1937, outbreaks occurred infrequently in humans until...
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