Human norovirus GII genotypic diversity in Gwangju, South Korea, based on ORF1-ORF2 junction (RdRp-VP1) analysis from 2020 to 2024.

This study analyzed human norovirus genogroup II (GII) strains detected in Gwangju, South Korea, between 2020 and 2024, focusing on genetic diversity and recombination at the ORF1-ORF2 junction involving the RNA-dependent RNA polymerase (RdRp, ORF1) and the major capsid protein VP1 (ORF2). Using year-round surveillance-based clinical samples, the analysis revealed that recombination events near the ORF1-ORF2 junction were a major driver of genotype replacement over time. Multiple recombinant lineages, including GII.4[P16], GII.17[P31], GII.3[P25], and the emergent, rarely reported genotype GII.7[P7], were detected during the study period. Although the RdRp gene is relatively conserved, sequence variation accumulating near the ORF1-ORF2 boundary may facilitate the emergence of new recombinant RdRp-VP1 combinations. These findings indicate that gene exchange at the ORF1-ORF2 junction plays a central role in shaping human norovirus genetic diversity.