Molecular epidemiology of enteroviruses associated with acute encephalitis syndrome in India

Background: Enteroviruses (EVs) are RNA viruses in the family Picornaviridae comprising more than 100 serotypes that are divided into four species, human enteroviruses A to D. The clinical manifestations of EVs range from conjunctivitis, respiratory tract infection, myocarditis, meningitis, encephalitis, and neonatal sepsis, like illness. Encephalitis is a rare presentation of EV infection, but many EV serotypes (coxsackievirus [CV] A9, A10, and B5, echovirus [ECV] 4, 5, 9, 11, 19, and 30, and EV 71, 75, 76 and 89) have been reported in encephalitis cases from different parts of the world. Genotyping of EV is important to establish clinical characteristics and epidemiological link. The objective of this study was to identify EV serotype involved in acute encephalitis syndrome cases occurred in northern India during 2011-2012. Methods & Materials: Molecular method targeting 5’ untranslated region (UTR) and VP1 capsid region was used for EV detection and identification in direct clinical specimen. Results: EV RNA was detected in 68 (28.7%) of 237 CSF samples by real time RT-PCR targeting the highly conserved 5’ UTR region. Molecular typing by RT-PCR and sequencing of a partial VP1 region revealed the predominance of ECV 19 (n = 41), followed by ECV 11 (n = 4), EV 76 (n = 3), CV B5, ECV 13, 21, EV 69 and EV 101 (n = 2 each), CV A2 and ECV 33 (n = 1 each). Phylogenetic analysis showed 0-2% divergence at nucleotide level among ECV 19. Conclusion: ECV 19 was the main etiologic agent involved in 2011 encephalitis epidemic. Molecular typing of EVs is useful for characterizing emerging serotypes and their epidemiological investigation.