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.