Increase of GII.17 Norovirus Infections During the 2024-2025 Season in Multiple Cities, China.

A significant numerical increase of genotype GII.17 norovirus-associated sporadic infections was observed in multiple cities in China during the 2024-2025 season. We collected fecal samples from hospitalized children with acute gastroenteritis from 29 sentinel hospitals nationwide to screen for norovirus. A total of 18.7% (n = 412) of the samples tested positive, with a decrease in genotype GII.4 (27% of all positive cases) coinciding with an increase in GII.17 (62%). Comparative phylogenetic analysis of RNA-dependent RNA polymerase and capsid gene sequences revealed that these GII.17[P17] strains were most closely related to strains circulating in the United States and European countries during 2023-2024, with which they shared a recent common ancestor. The evolving epidemiology of norovirus, characterized by the circulation of multiple genotypes, highlights the need for ongoing surveillance and research to better understand its impact and guide the development of vaccines.