Trend of Japanese encephalitis in North India: evidence from thirty-eight acute encephalitis cases and appraisal of niceties.

BACKGROUND In the year 2005, an epidemic of Japanese encephalitis (JE) occurred in the northern states of India. The present study was planned to reconfirm the circulation of JE in the area and to assess the trend of the disease to slow down the burden of JE. METHODOLOGY Surveillance was conducted to identify patients with acute encephalitis. Blood and cerebrospinal fluid specimens from suspected cases underwent pathological, serological, and demographic investigations. Viral testing for evidence of Japanese encephalitis virus (JEV) infection was also performed, either by IgM capture ELISA/RT-PCR or both. To identify circulating JEV strains, RT-PCR, sequencing and phylogenetic analysis was performed. Based on clinical cases reported between 1992 and 2008, the trend of JE infection in the state was analyzed to examine the dynamics of infection. RESULTS Our investigations (n = 38) revealed that only 55.3% cases were positive for JE. Pathological examination revealed marked pleocytosis in CSF (90+/-76.9 cells/mm(3)), and peripheral leucocytosis (64.7+/-8.86% neutrophils) with mild anemia. Males were more susceptible than females with a ratio of 1.63:1 and significant gender difference (P<0.05) was observed in patients below six years. In the patient group younger than six years, the rate of infection per million was six-fold higher (P<0.005) in males as compared to females. Our phylogenetic study suggests that the circulating strain during the 2005 JE epidemic was close to GP78, and in the future a larger epidemic may occur. CONCLUSIONS The 2005 JE epidemic was possibly caused by JEV GP78 and it is spreading into newer areas. The trend of JE suggests that the problem in North India is escalating and larger epidemics may occur in the future; therefore, serious steps are necessary to combat JE, including the development of more efficient surveillance methods and differential diagnosis.