Symptoms

- 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.

Treatment

- 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. 

Outcome

- 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.