Resurgence and Predominance of GII.17[P17] Norovirus in Children With Sporadic Acute Gastroenteritis in Shanghai, China.

Human norovirus has been identified as a significant causative agent of acute gastroenteritis on a global scale. We investigated the epidemiological of norovirus infections in children with acute gastroenteritis in Shanghai between January 2022 and December 2024. The overall prevalence of norovirus was 13.22% (281/2126), with annual rates of 3.77% (20/531) in 2022, 18.30% (149/814) in 2023, and 14.34% (112/781) in 2024. The 281 norovirus strains were classified into the GI group (0.71%, 2/281) and GII group (99.29%, 279/281). Phylogenetic analysis revealed that 90.39% (254/281) of HuNoV strains were successfully genotyped for both VP1 and RdRp genes, with 15 distinct genotype combinations. The most prevalent strain was GII.4 Sydney[P16] (52.36%, 133/254), followed by GII.17[P17] (21.26%, 54/254) and GII.3[P12] (11.42%, 29/254). Of note, GII.4 Sydney[P16] was observed in both 2022 (56.25%, 9/16) and 2023 (74.10%, 103/139), while GII.17[P17] emerged as the predominant genotype in 2024 (43.43%, 43/99). Furthermore, most of the GII.17[P17] strains identified in 2024 clustered with GII.17[P17] strains identified in the United States in 2025. These findings provide new insights into the genetic diversity of HuNoV and indicate a resurgence of a new GII.17[P17], which has become a leading cause of sporadic AGE in children in Shanghai.