Eastern equine encephalitis is found in North America, Central and South America, and the Caribbean. In the United States, most cases have been reported from the eastern seaboard states, the Gulf Coast, and some inland midwestern areas. The eastern equine encephalitis virus has a complex life cycle involving birds and a specific type of mosquito, Culiseta melanura , that lives in marshes and swamps. These mosquitoes can transmit the virus to animals and people. After infection, the virus invades the central nervous system, including the spinal cord and brain.
Infection can cause a range of illnesses.
For people with infection of the central nervous system, a sudden fever and severe headache can be followed quickly by seizures and coma. About half of these patients die from the disease. Of those who survive, many suffer permanent brain damage and require lifetime institutional care. Symptoms usually appear 4 to 10 days after the bite of an infected mosquito. Diagnosis is based on tests of blood or spinal fluid.