West Nile Virus Infection in Birds and Mosquitoes, New York State, 2000

Abstract

The emergence of West Nile (WN) virus in 1999 in four U.S. states (1) was followed by its spread to 12 states in 2000 (2). An enzootic cycle was established between birds and mosquitoes, and WN disease was observed in humans, horses, and birds in both years (2,3). Bird deaths due to WN virus are unusual outside North America, with the exception of deaths of geese in Israel (4) and pigeons in Egypt (5). In 1999 in North America, WN disease, characterized by meningoencephalitis and myocarditis, was observed in 14 species of wild and captive birds (6). WN virus has been detected in a number of mosquito genera in North America, including Culex and Aedes species (2,7). Vector competence has been confirmed experimentally for some North American species, including Cx. pipiens, Ae. vexans, and Ae. japonicus (8,