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

## TL;DR

Norovirus infections caused by the GII.17 genotype increased significantly in China during the 2024–2025 season, replacing the previously dominant GII.4 genotype.

## Contribution

The study identifies a shift in norovirus genotype prevalence and links GII.17 strains to those circulating in the US and Europe.

## Key findings

- GII.17 norovirus accounted for 62% of positive cases, while GII.4 dropped to 27%.
- Phylogenetic analysis showed GII.17 strains shared a recent ancestor with strains from the US and Europe.
- The study highlights the need for ongoing surveillance due to the evolving norovirus epidemiology.

## Abstract

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.