Summary

Eastern Equine Encephalitis (EEE) is a severe mosquito‑borne viral disease affecting horses and humans. The virus circulates between birds and mosquitoes, with horses and people becoming infected after mosquito bites but not transmitting the disease further. EEE occurs most commonly in the southeastern United States and is most dangerous for young or unvaccinated horses. The incubation period in horses is typically 3–7 days, and up to 90% of infected horses die. Clinical signs in horses include fever, stiffness, hypersensitivity, behavior changes, neurologic abnormalities, recumbency, and death. Diagnosis is based on clinical signs and antibody testing. There is no cure, and treatment is supportive. Prevention relies on regular vaccination and aggressive mosquito control measures.