Japanese B Encephalitis

Japanese B encephalitis, a zoonotic viral disease, is the only identified virus leading to epidemic encephalitis in India. The disease, spread by culicine mosquitoes, is maintained in animals and birds, particularly pigs and ardied birds, humans being dead-end hosts. Worldwide, approximately 35,000-50,000 symptomatic cases develop per year. Most of the infected cases remain subclinical and out of the symptomatic patients only a minority develop neurologic dysfunction. The incubation period ranges from 4-14 days, which is followed by a prodrome of fever, headache, nausea followed by altered mental status and neurologic features like seizures. Infection can be identified by isolation of virus, detection of antigen or detection of antibody. IgM captured Enzyme Linked Immunosorbant Assay, New IgM dot enzyme immunoassays, Reverse passive haemagglutination, polymerase chain reaction and other methods of antibody detection can be used. Therapy for symptomatic Japanese encephalitis infection is supportive. Mortality rates in places with intensive care capabilities are 5-10%. In less developed areas, mortality rates may exceed 35%. Worldwide, more than 10,000 reported deaths occur per year. Approximately 33-50% of patients with symptomatic disease who survive have major neurologic sequelae at 1 year, including seizure disorders, motor or cranial nerve paresis, or movement disorders. Other than the means to avoid mosquito exposure, an effective and immunogenic vaccine, now easily available in India, can be used as an effective preventive measure against Japanese encephalitis.