Since the incubation period (interval from infection to the onset of symptoms) is believed to range between from 4-14 days and in some case, the incubation period being as long as 45 days, the disease manifests with intense severity. Most people who survive acute encephalitis make a full recovery, but long term neurological conditions have been reported in survivors. Approximately 20% of patients are left with residual neurological consequences such as seizure disorder and personality changes. A small number of people who recover subsequently relapse or develop delayed onset encephalitis. The case fatality rate is estimated at 40% to 75%; however, this rate can vary by outbreak depending on local capabilities for epidemiological surveillance and clinical management.
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