Epizootiology of eastern equine encephalitis virus in upstate New York, USA. VII. Virus surveillance 1978-85, description of 1983 outbreak, and series conclusions.

Abstract

Mosquito and arbovirus surveillance activities have been routinely conducted in upstate New York since 1971. This report details the surveillance results during 1978–85. Minimal virus activity was detected in the first 4 yr of concentrated surveillance at Toad Harbor Swamp, Oswego County. In 1983, an outbreak of eastern equine encephalitis (EEE) resulted in one human and nine equine cases. The outbreak was preceded by an epiornitic of Highlands J (HJ) virus in 1982; this was the first evidence of HJ virus activity in the region. Isolations of EEE virus from mosquitoes in 1983 incriminated Culiseta melanura (Coquillett) and Cs. morsitans (Dyar) as epiornitic vectors and Aedes canadensis (Theobald) as an epizootic vector. Mosquito collection data from two endemic foci indicated substantial and significant differences in EEE virus infection rates. The occurrence of HJ virus, the differences in mosquito infection rates, and widespread epizootic disease during a year of low mosquito densities are used to develop a hypothesis on the distribution of multiple endemic foci of EEE virus in upstate New York.