Genetic epidemiology of porcine epidemic diarrhoea virus circulating in China in 2012-2017 based on spike gene

A porcine epidemic diarrhoea outbreak first occurred in southern China at the end of 2010 and afterwards the disease spread throughout the country. Spike gene is divergent and important for understanding the genetic relations of porcine epidemic diarrhoea virus field strains, the epidemiological status of the virus and vaccine development. In this study, S1 regions of spike gene of 1,235 selected strains collected from 2012 to 2017 in China were clustered along with 25 references of spike sequences mainly from China. The phylogenetic analysis demonstrates that these sequences of S1 regions were genetically more diverse with time. In all strains, G1a, G1b, G2a and G2b clusters accounted for 1.9%, 9.6%, 32.2% and 56.3%, respectively, namely G2a and G2b were the two most prevalent clusters in China. Furthermore, we made a more detailed classification for G2 group based on phylogenetic tree, in which G2a was divided into two subgroups, and G2b was separated into four subgroups.