Symptoms of Eastern Equine Encephalitis

For Everyone

Key points

  • Eastern equine encephalitis virus can cause a mild illness or severe disease, including meningitis or encephalitis.
  • Most people have no or mild symptoms, but severe illness can result in long-term complications and death.
  • Talk to your healthcare provider if you think you or a family member might have eastern equine encephalitis.
A patient holds a digital thermometer.

Symptoms

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

Eastern equine encephalitis virus infection can result in mild illness (febrile) or severe (neurologic) disease. The type of illness will depend on the age of the person and other factors.

Mild illness

Symptoms of mild illness can include:

  • Fever
  • Chills
  • Body aches
  • Joint pain

The illness lasts 1 to 2 weeks, and most people recover completely when there is no central nervous system involvement.

Severe illness

Symptoms of severe illness can include meningitis (inflammation of the membranes that surround the brain and spinal cord) or encephalitis (inflammation of the brain).

  • Fever
  • Headache
  • Vomiting
  • Diarrhea
  • Seizures
  • Behavioral changes
  • Drowsiness
  • Coma

In infants, severe illness often occurs soon after onset. In older children and adults, encephalitis might occur after several days of systemic illness.

Treatment

No medicines are available to treat eastern equine encephalitis. Rest, fluids, and over-the-counter pain medications may relieve some symptoms.

Outcomes and complications

Approximately a third of all people who develop severe illness 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 problems. These can range from mild to severe intellectual disability, personality disorders, seizures, paralysis, and cranial nerve dysfunction.

People with severe disease and ongoing disabilities often require long-term care and die within a few years.

For Health Care Providers Clinical Signs and Symptoms of Eastern Equine Encephalitis

Testing and diagnosis

If you think you or a family member might have eastern equine encephalitis, talk to your healthcare provider.

Healthcare providers diagnose eastern equine encephalitis based on:

  • Signs and symptoms
  • History of living in or traveling to an area where eastern equine encephalitis virus is known to circulate
  • History of possible exposure to the mosquitoes that can spread eastern equine encephalitis virus
  • Laboratory testing

Your healthcare provider can order tests to look for eastern equine encephalitis virus or other infections that can cause similar symptoms.

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Content Source:
National Center for Emerging and Zoonotic Infectious Diseases (NCEZID)