West Nile Virus Outbreak Among Horses in New York State, 1999 and 2000

Abstract

An outbreak of arboviral encephalitis attributable to West Nile (WN) virus was first recognized in the United States in 1999, when dead crows were reported in and near New York City, and a zoological park noted that some of their exhibition birds had died. These events coincided with initial public health reports of human encephalitis cases diagnosed as St. Louis encephalitis virus in New York City (1). The successful isolation of virus from dead birds allowed the subsequent identification of WN virus as the etiologic agent of both human and animal disease (2).