Eastern equine encephalitis (EEE) is a rare but serious viral disease spread by mosquitoes that can affect people and horses. EEE can also cause disease in captive birds such as the ring-necked pheasant, emu, ostriches, quail and ducks. EEE infection and disease can occasionally occur in other livestock, deer, dogs, other mammals, reptiles and amphibians. EEE is transmitted by the bite of an infected mosquito. Mosquitoes become infected by feeding on infected birds. Infected mosquitoes will then occasionally feed on horses, humans and other mammals. Several species of mosquitoes can become infected with the EEE virus (EEEV). EEE is not spread person-to-person, from people to animals or from animals (other than mosquitoes) to people. Most people bitten by an infected mosquito will not develop any symptoms. Severe cases of EEE infection begin with the sudden onset of headache, high fever, chills, and vomiting. The illness may then progress into disorientation, seizures, encephalitis (inflammation of the brain) and coma. Approximately a third of patients who develop EEE die, and many of those who survive have mild to severe brain damage. It takes 4-10 days after the bite of an infected mosquito to develop symptoms of EEE.
The physical examination for EEE also is nonspecific, yielding findings similar to those seen with many other encephalitides.Changes in vital signs may include the following:
• Possible tachypnea
Neurologic findings may include the following:
• Bilateral papilledema
• Nuchal rigidity
• Focal sensory or motor deficit
• Depressed or hyperactive reflexes
• Tremors EEE is a summertime disease and most commonly affects people younger than 15 years and older than 55 years.
The exact reason for this pattern is not known, but the preference for extremes of age is a characteristic common to many species of the alphavirus family. Patient age does not affect prognosis, but permanent neurologic impairment and death are more common in children.