Increasing trend of Japanese encephalitis cases in West Bengal, India – a threat to paediatric population

ObjectiveTo detect the Japanese encephalitis virus (JEV) as the etiologic agent from the acute encephalitis syndrome (AES) cases mainly amongst the children and young adults from vaccinated and non-vaccinated districts of West Bengal.MethodsFor the detection of JEV, a total of 828 sera were referred from vaccinated and non vaccinated districts of West Bengal during 2005-2011. Japanese encephalitis (JE) positive cases were confirmed by ELISA and RT-PCR method.ResultsOut of 828 cases, 245 samples were positive by ELISA method and 46 samples were positive by RT-PCR method. Out of 291 total positive cases, 162 (55.6%) were below 20 years of age. Initially in 2005, JE cases were highest amongst the children and young adults (0-20 years). After vaccination, although the JE cases declined gradually in the vaccinated districts, but again from 2010, JE cases from the said age group showed an increasing trend from those districts. JE cases were also reported from other endemic zones of this state, which were still non-vaccinated.ConclusionsIn West Bengal, JE cases are still predominated among children and young adults till the year 2011. Mass scale vaccination programme and investigation on the circulating strains are essentially required to find out the reasons of increasing tendency of JE cases in this state.