Humans and other mammals are dead end viral host incapable of directly transmitting the disease to other organisms. Infection can also occur through direct contact with brain or spinal cord matter of infected animals. Asymptomatic infections are not uncommon, but systemic symptoms including high fever, headache, chills, vomiting, malaise, and myalgia often manifest four to 10 days post infection. Severe, encephalitic infections results in fever, irritability, drowsiness, seizuures, disorientation, vomiting, anorexia, diarrhea, convulsions, coma, and death. With an overall case fatality rate of approximately 33 percent, EEE often results in death two to 10 days after symptom onset. Those with systemic, non-encephalitic infections often recover in one to two weeks, but those with severe infections are often left with intellectual impairment, paralysis, seizures, and personality dysfunction. Most patients with severe infections that do not die immediately after symptom onset die due to sequelae within several years. No vaccines currently exist for EEE and treatment is symptomatic.