September 3, 2019

Eastern Equine Encephalitis Positive Horse

The purpose of this health advisory is to alert clinicians to the potential for human Eastern Equine Encephalitis (EEE) disease activity in Maine and to consider testing for EEE in patients presenting with unexplained encephalitis, meningitis or high fever (100.4F or 38C) during the summer and early fall.

Maine Department of Agriculture, Conservation, and Forestry notified Maine CDC of a case of Eastern Equine Encephalitis (EEE) in a horse from York County late Friday August 30th. The Animal Health Diagnostic Center at Cornell University in New York confirmed the EEE result in this horse. Maine has not detected EEE to date in mosquito collections. However, public health officials in other Northeast states have seen significant increases in EEE activity this year. Massachusetts has reported four human cases and one human death, as well as four animal deaths from EEE. New Hampshire has reported one animal death from EEE. Maine has not identified a human case of EEE since 2015.

EEE is a rare, but potentially fatal arboviral disease. It is the most severe arboviral infection found in the United States. EEE virus is transmitted to humans through the bite of an infected mosquito. Signs and symptoms can include fever, headache, myalgias, vomiting, weakness, confusion, seizures, and memory loss. In more serious cases, the illness may progress to encephalitis, coma, and death. The case-fatality rate for infected individuals is approximately 33% and up to 50% for those who show symptoms. Most survivors are left with significant and long-term brain damage. Symptoms can begin anytime from four to ten days after the mosquito bite, and usually last one to two weeks. It is possible some people will not show any signs of EEE illness. There is no specific treatment, but people with severe EEE illness often need to be hospitalized.

Advisory (PDF)