Nervous System Home > Viral Encephalitis

Often resulting in swelling of the brain, viral encephalitis is a group of diseases transmitted to humans by an insect bite. Different types include West Nile virus, Japanese encephalitis, and St. Louis encephalitis. Symptoms of encephalitis typically begin with fever and severe headache, and may then progress to symptoms such as vomiting, sensitivity to light, and seizures. There are no human vaccines for this group of illnesses, except for a Japanese encephalitis vaccine that is available only to travelers.

What Is Viral Encephalitis?

Viral encephalitis is a group of illnesses that can cause swelling of the brain (encephalitis). The illnesses are transmitted to humans by insects that bite, such as ticks and mosquitoes.


Types of viral encephalitis include:

Symptoms of Viral Encephalitis

Symptoms of viral encephalitis usually begin with fever and a severe headache.
Symptoms that follow the fever and severe headache may include:
  • Sensitivity to light
  • Nausea and vomiting
  • Stiff neck and back
  • Lack of energy
  • Drowsiness
  • Seizures or tremors
  • Change in personality
  • Memory loss
  • Trouble learning and/or understanding
  • Restlessness
  • Confused speech
  • Hallucinations
  • Coma.
Milder viral encephalitis symptoms are often caused by less serious diseases and normally should be no cause for alarm. In general, symptoms that develop suddenly and are severe from the start tend to be associated with more severe, life-threatening cases of encephalitis.
Early encephalitis may also cause symptoms similar to meningitis, a serious illness that causes inflammation of the tissues surrounding the brain and spinal cord.
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Last reviewed by: Arthur Schoenstadt, MD
Last updated/reviewed:
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