A Descriptive Study of Japanese Encephalitis in West Bengal, India, Based on Surveillance Data: Changing Pattern Observed in Recent Years

Japanese encephalitis (JE), commonly affects children and is a major cause of acute childhood encephalopathy. Growth of population, intensified rice farming, pig rearing and lack of surveillance are the key factors for transmission of the disease. Although various hospital and laboratory based studies have been conducted on epidemiology of JE in various parts of India including West Bengal, still the need for further research to have a much clear understanding of this disease epidemiology is beyond any question. The present study aimed at determining the Sample Positivity Rate (SPR) and distribution (Time, Place, Person) of JE cases in West Bengal. This descriptive study was conducted over 9 months periods (June 2012 – February 2013), based on surveillance data corresponding to years 2011& 2012, collected from different JE screening Sentinel Laboratories of West Bengal. Confirmation of JE was done by IgM ELISA method. SPR was significantly higher for older age groups. Mean age of JE cases were significantly higher in 2012. Cases were also found consistently in 2011-12 in districts of North Bengal such as Jalpaiguri, Dakshin Dinajpur, Coochbehar etc. Two different peaks were observed in Epi Curve i.e. for northern part, during July August and for southern part, during October – November. JE has been found to be significantly affecting older age groups as well as people of North Bengal districts of West Bengal in recent years. Also different seasonal pattern has been playing role in transmission of JE in different parts of West Bengal.