Molecular investigations of chikungunya virus during outbreaks in Orissa, Eastern India in 2010

► Unprecedented chikungunya outbreaks were reported in Orissa, Eastern India in 2010. ► Aedes albopictus was the major vector of CHIKV in this region. ► CHIKV strains of Indian Ocean lineage of ECSA genotype was the etiological agent. ► CHIKV with E1-A226V, E2-L210Q and E2-I211T mutations were circulating in Orissa. ► Circulation of mutant CHIKV led to periodic re-emergence of chikungunya in Orissa.