The Region-Specific Genetic Relationship and Mutation Characteristics of Viral Hemorrhagic Septicemia Virus

Since viral hemorrhagic septicemia virus (VHSV) was first identified in rainbow trout, it has evolved into four major genotypes in the process of infecting multiple hosts. The different levels of virulence among genotypes of VHSV are caused by genetic evolution. In this study, the complete genome sequences of global VHSV strains were obtained from the GenBank database and their genetic relationships were analyzed. The maximum likelihood (ML) phylogenetic tree based on the complete genomes of VHSV showed that globally, VHSV strains evolved into two region-specific clades, namely the European clade and the North American clade. North American VSHV strains are more conserved than European strains. Both European and North American strains are subjected to purifying selection. All VHSV proteins are gathered into their region-specific clusters in genetic distance space. Furthermore, North American and Asian strains have organized glycosylation sites in their G protein. An early Japanese strain, KRRV9822, which clusters into the North American clade, has undergone potential recombination. Together, the region-specific genetic relationship and mutation characteristics of global VHSV strains were revealed with a crucial perspective for epidemiological research on VHSV.