Serotypic and genotypic profile of dengue virus outbreaks in India between 2011 and 2017

The epidemiology of dengue has been demonstrating significant changes in recent years, with rising incidence of infection in countries with known endemicity and occurrence of fresh outbreaks in previously unaffected territories. India, which has been a traditional hotspot dengue virus (DENV) transmission in the endemic south-east Asian region, has been affected by the sweeping changes in dengue epidemiology. Two remarkable developments characterize the alterations witnessed by India from 2011-2017. First, all parts of the country have witnessed abrupt replacement of existing DENV lineages with emerging novel strains. Second, co-circulation of multiple serotypes of DENV have been reported from all across the country from 2011-2017; thereby hinting at the transition of the country towards hyper-endemicity. Considering the potential clinical implications of such epidemiological transformation in terms of increasing involvement of pediatric patients and growing predisposition to serious complications, the present review provides an update on the serotypic and genotypic profile of dengue outbreaks that have been witnessed by different zones of India between 2011 and 2017. Dividing the country into northern, southern, eastern, western, central and north-eastern zones, we describe discrete zone-specific distribution patterns of DENV serotypes and genotypes and observe simultaneous circulation of different DENV strains in different parts of the country. Random shifts in the genetic characteristics of the circulating strains and widespread co-circulation of all four serotypes underscore the need for undertaking continuous and representative molecular surveillance of the circulating DENV strains across the country for prompt identification of emerging strains and novel mutants; gain insights into the formulation of dengue vaccines and develop a clearer understanding of the molecular basis of immune evasion, disease epidemiology and pathogenesis.