Status and trend of acute encephalitis syndrome and Japanese encephalitis in Bihar, India.

BACKGROUND.: Acute encephalitis syndrome (AES) is a clinical condition, of which the most common cause is Japanese encephalitis (JE). Though there is deficiency of data on AES and JE from Bihar, the state ranks third in the reporting of JE cases after Uttar Pradesh and Assam. We aimed to assess the status and trends of AES and JE cases in Bihar and to know the status of the disease in the districts. METHODS.: We collected monthly epidemiological data for AES and JE for the period 2009-2014. RESULTS.: A total of 4400 cases (733 cases/year) with an average case fatality rate (CFR) of 30% for AES for the entire study period. A total of 396 cases of JE were reported with approximately 14% CFR. The disease peaks were during the start and end of the Indian summer and monsoon months for AES and JE, respectively. Districts such as Patna, Jehanabad, Nawada, Gaya and East Champaran reported the maximum number of AES and JE cases with annual incidence rates of 4.7-25.0 and 0.546-1.78 per 100 000 population, respectively. CONCLUSION.: Since 2009, the incidence of AES and JE cases has been increasing in Bihar.