West Nile Virus Outbreak Among Horses
West Nile Virus Outbreak Among Horses
West Nile (WN) virus was identified in the Western Hemisphere in 1999. Along with human encephalitis cases, 20 equine cases of WN virus were detected in 1999 and 23 equine cases in 2000 in New York. During both years, the equine cases occurred after human cases in New York had been identified.
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. 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.
WN virus is primarily transmitted between mosquitoes and birds, but transmission to mammals can occur when infection occurs in mosquito species that feed on birds and mammals. Encephalitis has been confirmed only in humans and horses. During 1999, 20 equine cases of WN virus encephalitis were confirmed in the United States, all in New York. In 2000, 23 equine cases were identified in New York, with more cases identified in New Jersey, Delaware, Rhode Island, Massachusetts, Connecticut, and Pennsylvania. We summarize these findings.
West Nile (WN) virus was identified in the Western Hemisphere in 1999. Along with human encephalitis cases, 20 equine cases of WN virus were detected in 1999 and 23 equine cases in 2000 in New York. During both years, the equine cases occurred after human cases in New York had been identified.
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. 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.
WN virus is primarily transmitted between mosquitoes and birds, but transmission to mammals can occur when infection occurs in mosquito species that feed on birds and mammals. Encephalitis has been confirmed only in humans and horses. During 1999, 20 equine cases of WN virus encephalitis were confirmed in the United States, all in New York. In 2000, 23 equine cases were identified in New York, with more cases identified in New Jersey, Delaware, Rhode Island, Massachusetts, Connecticut, and Pennsylvania. We summarize these findings.