Characterization of unusual DS-1-like G3P[8] rotavirus strains in children with diarrhea in Japan

The emergence and rapid spread of novel DS-1-like intergenogroup reassortant rotaviruses having the equine-like G3 genotype (DS-1-like G3P[8] strains) have been recently reported from several countries. During rotavirus surveillance in Japan in 2015–2016, three DS-1-like G3P[8] strains were identified from children with severe diarrhea. In the present study, we sequenced and characterized the full genomes of these three strains. On full-genomic analysis, all three strains showed a unique genotype constellation including both genogroup 1 and 2 genes: G3-P[8]-I2-R2-C2-M2-A2-N2-T2-E2-H2. Phylogenetic analysis revealed that each of the 11 genes of the three strains was closely related to that of Japanese DS-1-like G1P[8] and/or Japanese equine-like G3P[4] human strains. Thus, the three study strains were suggested to be reassortants that acquired the G3-VP7 gene from equine G3 rotaviruses on the genetic background of DS-1-like G1P[8] strains. Our observations will provide important insights into the evolutionary dynamics of emerging DS-1-like G3P[8] strains.