Molecular genetic characterisation of norovirus GII.17 strains circulating in South Korea in 2024

BACKGROUND In South Korea, norovirus outbreaks have been predominantly attributed to the GII.4 genotype; however, since mid-2024, strains harbouring the GII.17 genotype are being detected more frequently, raising concerns about a potential shift in the dominant circulating strain and resulting public health implications. AIM We aimed to analyse the nt sequences of the gene encoding the viral protein 1 (VP1), the major capsid protein, of the GII.17 norovirus strains detected in South Korea in 2024, compare them with the corresponding nt sequences of the GII.17 Kawasaki 2014 lineage strains and evaluate whether GII.17 has the potential to replace the long-dominant GII.4 genotype. METHODS We obtained 11 complete VP1 sequences from stool specimens collected across six regions in South Korea (Busan, Daejeon, Gangwon-do, Gyeongsangbuk-do, Incheon, Jeollanam-do) in 2024 and compared them with the VP1 sequence of the reference strain (GII.17 Kawasaki 2014) to identify genetic changes. RESULTS Key amino acid substitutions (R299P, N378D and K388R) were identified in the P2 domain of the VP1, which is a major antigenic site. Notably, N378D corresponds to D374 in the GII.4 genotype, which is a position involved in histo-blood group antigen (HBGA) binding, and K388R, adjacent to other antigenic sites, may alter the surface charge of the capsid. CONCLUSION The data provide molecular evidence that the emerging GII.17 strain in South Korea may evade the host immune surveillance machinery and exhibit altered receptor binding, underscoring the public health threat posed by this strain and the need for enhanced genomic surveillance and effective vaccine development.