CLIMATE AND THE RE-EMERGENCE OF EASTERN EQUINE ENCEPHALITIS IN THE NORTHEASTERN USA

Eastern equine encephalitis is a mosquito-borne viral disease endemic in the northeastern US. Though primarily a disease of horses, human cases do occur and the case fatality rates are high. Human cases are rare. Until 2003, cases occurred sporadically in New York, Massachusetts, Rhode Island, and New Jersey with an average of 1.32 (st dev 2.31) cases per year – often with no cases occurring between outbreak years. Over the last decade however, virus activity resulting in human and equine cases has expanded northward into Vermont and New Hampshire and no years have been without at least one human case (mean number of cases per year since 2003 = 4.20, st dev 3.29). The explanation for the shift from a sporadic to regular pattern of cases and the spread into new areas is unknown. We describe the observed pattern in greater detail and present findings with respect to the climate drivers of this re-emerging disease.