Incidence of Japanese Encephalitis amongst acute encephalitis syndrome cases in upper Assam districts from 2012 to 2014: A report from a tertiary care hospital

Background & objectives: Japanese encephalitis (JE) is a major public health problem in India because of high mortality rate and residual neuropsychiatric damage in the survivors. The present study was undertaken to investigate JE positivity amongst patients admitted with acute encephalitis syndrome (AES) in upper Assam districts and different parameters with their changing trends related to it. Methods: It was a hospital-based prospective cross-sectional study conducted from January 2012 to December 2014. A total of 1707 consecutive non-repetitive hospitalized patients, satisfying the clinical case definition of AES as per the WHO guidelines, were included in the study. Cerebrospinal fluid (CSF) and serum samples were tested for JEV-specific IgM antibodies. Results: Of the 1707 patients admitted, 696 (40.77 %) were diagnosed as JE with male-to-female ratio 1.7: 1 and adult to paediatric ratio 2.2: 1. Fever (100%), change in mental status (100%), headache (80.02%), neck rigidity (52.01%), unconsciousness (48.99%), seizure (37.64%) and paralysis (11.06%) were the major clinical findings. The majority of cases (94%) were from rural areas. There was a significant association of JE cases with rainy season of the year i.e., June to August (P<0.001). Overall, 14.94 per cent deaths were reported in JE positive cases. Interpretation & conclusions: A higher occurrence of JE was observed in above 15 yr age group. Cases were mainly from rural areas, and there was clustering of cases in rainy season.