Symptoms, Diagnosis, & Treatment

Symptoms

Most people infected with eastern equine encephalitis (EEE) virus do not develop symptoms. For those who develop symptoms, the time from infected mosquito bite to onset of illness (incubation period) ranges from 4 to 10 days.

EEE can result in febrile illness (fever) or neurologic disease, including meningitis (infection of the membranes that surround the brain and spinal cord) or encephalitis (infection of the brain). The type of illness will depend on the age of the person and other factors.

Febrile illness is characterized by fever, chills, body aches, and joint pain. The illness lasts 1 to 2 weeks, and most people recover completely when there is no central nervous system involvement.

Signs and symptoms of neurologic disease include fever, headache, vomiting, diarrhea, seizures, behavioral changes, drowsiness, and coma. In infants, neurologic disease often occurs soon after onset; in older children and adults, encephalitis may occur after several days of systemic illness.

• Approximately a third of all people with encephalitis due to EEE die. Death usually occurs 2 to 10 days after onset of symptoms but can occur much later.
• Many people who recover are left with long-term physical or mental impairments, which can range from mild brain dysfunction to severe intellectual impairment, personality disorders, seizures, paralysis, and cranial nerve dysfunction.
• People with severe impairments often require long-term care and die within a few years.

Diagnosis

If you think you or a family member might have EEE, talk with your health care provider.

• Healthcare providers diagnose EEE virus infection based on:
  • Signs and symptoms
  • History of living in or traveling to an area where EEE virus is known to circulate
  • History of possible exposure to the mosquitoes that can carry EEE virus
  • Laboratory testing of blood or spinal fluid
• Your healthcare provider can order tests to look for EEE virus infection or other infections that can cause similar symptoms.

To learn more about testing, visit our Healthcare Providers page.

Treatment

• There are no medications to prevent or treat EEE virus infections. Antibiotics are not effective against viruses, such as EEE virus.
• Rest, fluids, and over-the-counter pain medications may relieve some symptoms.
• For severe disease, patients often need to be hospitalized to receive supportive treatment, such as intravenous fluids, pain medication, and nursing care.

To learn more about treatment, visit our Healthcare Providers page.