September 14, 2019 Mount Holyoke News Health & Science EEE in Massachusetts: South Hadley community at high risk level September 14, 2019 Mount Holyoke News Health & Science Eastern Equine Encephalitis (EEE) is an extremely rare, mosquito-transmitted disease first identified in Massachusetts in 1938. According to 7News Boston, there had been seven reported cases of EEE in Massachusetts as of Sept. 6.