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Symptoms & Treatment


  • Less than 1% of people infected with Japanese encephalitis (JE) virus develop clinical illness.
  • In persons who develop symptoms, the incubation period (time from infection until illness) is typically 5-15 days.
  • Initial symptoms often include fever, headache, and vomiting.
  • Mental status changes, neurologic symptoms, weakness, and movement disorders might develop over the next few days.
  • Seizures are common, especially among children.


  • No specific treatments have been found to benefit patients with JE, but hospitalization for supportive care and close observation is generally required.
  • Treatment is symptomatic. Rest, fluids, and use of pain relievers and medication to reduce fever may relieve some symptoms.  


  • Among patients who develop encephalitis, 20% - 30% die. 
  • Although some symptoms improve after the acute illness, 30%-50% of survivors continue to have neurologic, cognitive, or psychiatric symptoms.