Infection with EEE is asymptomatic in about 95% of cases, but severe cases are seen, with a mortality rate of 33%. A high fever, headache, and vomiting are the beginnings of inflammation of the brain. It can progress to disorientation, seizures, and/or coma. Significant brain damage can be seen in survivors. Immunity is lifelong.
In the United States, an average of 11 cases are reported annually. In 2024, 9 states reported cases with a total of 19 cases. Most illness with EEE occurs from June to October.
There is no treatment beyond supportive measures and there is no vaccine is available.
