ABSTRACT Noroviruses are a major cause of acute gastroenteritis worldwide. In Beijing, norovirus GII. 17 outbreaks, which dominated in 2014–2015 (66. 7%), surged again from 1. 3%–12. 2% (2015–2024) to 81. 7% (2024–2025), with reported outbreaks during July 2024–February 2025 dramatically exceeding the prior year (301 vs. 103). From 2014 to 2025, 249 GII. 17 outbreaks were identified, comprising 107 Kawasaki308 (1525 cases) and 142 Romania‐2021 (1840 cases) based on phylogenetic analysis. The proportion of outbreak settings differed for Romania‐2021 and Kawasaki308: kindergartens (35. 2% vs. 37. 4%), primary schools (46. 5% vs. 29. 0%), middle schools (5. 6% vs. 12. 1%) and others (12. 7% vs. 21. 5%). Romania‐2021 cases were younger and had more vomiting than Kawasaki308 cases. Phylogenetic analysis revealed that novel GII. 17 strains dominated in Beijing in 2024–2025 clustered with contemporaneous global strains, forming a distinct subcluster (New₂023–2025) within New (Romania‐2021 like) cluster. This subcluster exhibited unique amino acid substitutions in VP1, VP2 and non‐structure proteins compared to other clusters and New subclusters. Our findings confirm the dominance of Romania‐2021 like strains during 2024–2025 in Beijing. Differences in symptom profiles and affected age groups between Kawasaki308 and Romania‐2021, and unique amino acid substitutions may help explain the rapid predominance of the emerging cluster.
Li et al. (Thu,) studied this question.