Eastern equine encephalitis (EEE), also called triple E and sleeping sickness, is a viral disease caused mainly by the Eastern equine encephalitis virus (EEEV). Most infections in humans are asymptomatic, but about 5% of the time the infection progresses to severe neuroinvasive disease. Symptoms typically appear 3–10 days after being bitten by an infected mosquito and initially include fever, headache, nausea, vomiting, fatigue, muscle pain, and joint pain. Neurological symptoms usually appear a few days later and include altered mental state, encephalitis, photophobia, seizures, paralysis, and loss of consciousness and coma. The case fatality rate is 30–75% depending on age, with disease severity greatest in young children and the elderly. About 50 to 90% of survivors experience long-term neurological complications that range from minor to severe. EEE is most common in horses, in which the disease carries a 70–90% case fatality rate and permanent brain damage for survivors.