Outbreaks and sporadic cases of japanese encephalitis in the state of Odisha, India: Outcome of 7 years of laboratory surveillance

Acute encephalitis syndrome (AES) is a major public health challenge in India. We report here the epidemiology of sporadics and outbreaks of Japanese Encephalitis (JE) in Odisha state during 2012-2018. A total of 4235 AES cases (sporadics - 3394, outbreak cases - 841) recorded including 42 outbreaks; majority (n = 18) of which were during 2016. Overall JE virus (JEV) positivity was 11.78% (outbreak cases - 24.5%, sporadic cases - 8.6%). Age =15 years were largely affected during outbreaks, while 16-60 years population was dominant among sporadics. The major outbreak (2016) involved 336 patients from a tribal dominated district, spread over 173 villages. JEV seropositivity was high (43.45%) with 28.57% mortality. Epidemiological linkage with pig rearing was documented through JEV neutralizing antibodies in 50% of pig serum samples. Although the postvaccination period (2017-18) showed increase in AES case reporting but low JE proportion. Ongoing surveillance and preparedness of the health system would be of importance, especially in tribal-dominated districts.