Japanese encephalitis in and around Pondicherry, South India: a clinical appraisal and prognostic indicators for the outcome.

Japanese encephalitis (JE) is numerically one of the most important causes of viral encephalitis worldwide, with an estimated 50,000 cases and 15,000 deaths annually. About one-third of patients die and half of the survivors have severe neuropsychiatric sequelae. Three hundred patients clinically suspected of JE were tested in the present study. Laboratory confirmation of JE was on the basis of detection of antigen or presence of JE-specific IgM antibody and/or neutralizing antibody in a single CSF sample. The risk factors that were associated with fatal outcome were determined. Japanese encephalitis infection was confirmed in 70.7 per cent (212/300) of the patients. All patients were from rural areas and with low socioeconomic background. Prominent clinical findings were: fever in 100 per cent (212/212) patients, altered sensorium in 87.73 per cent (186/212), convulsion in 85.84 per cent (182/212), headache in 50 per cent (106/212), and vomiting in 47.64 per cent (101/212). The final clinical outcome was available for only 68.39 per cent (145/212) of patients, as children were taken home against medical advice. Of these, 35.86 per cent (52) died while 63.44 per cent (92) of patients survived. Correlations of investigative findings with the final outcome revealed that absence of virus-specific IgM and neutralizing antibodies in CSF were associated with fatal outcome. In patients diagnosed with Japanese encephalitis the presence of a virus-specific immune response is associated with a favourable outcome and an important parameter in recovery from illness.