West Nile virus was first reported in Uganda in 1937. WNV is a zoonosis, with "spill-over" to humans, which also poses significant risks for wildlife, zoo and domestic animal populations. While it is not known how West Nile virus (WNV) entered the New World in 1999, anomalous weather conditions may have helped amplify this Flavivirus that circulates among urban mosquitoes, birds and mammals. We analyzed weather patterns coincident with a series of U.S. urban outbreaks of St. Louis encephalitis (SLE), (a disease with a similar life cycle), and four recent large outbreaks of WNV. Drought emerged as a common feature. As the potential risks from pesticides for disease control must be weighed against the health risks of the disease, an early warning system of conditions conducive to amplification of the enzootic cycle could help initiate timely preventive measures, and potentially limit chemical interventions.
KeywordsEncephalitis Early Warning West Nile Virus Domestic Animal Warning System
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