Global trends in norovirus genotype distribution among medically attended children with acute gastroenteritis, 2020-2025.

Abstract

BACKGROUND: Norovirus is a leading cause of acute gastroenteritis, with a broad diversity of genotypes infecting children. NoroSurv is an established global network for norovirus strain surveillance among medically attended children < 5 years of age.

METHODS: Participating laboratories uploaded norovirus sequences from stool specimens collected from 2020 to 2025 to a web portal, which assigned norovirus genotypes and strain data. Norovirus seasons were defined as September 1 to August 31.

RESULTS: Participants in 22 countries across 6 continental regions uploaded 4113 norovirus sequences, including 26 genotypes and 53 strains. GII.4 accounted for 53% (2167/4113), followed by GII.3 (12%), GII.17 (11%), GII.6 (7%), and GII.2 (5%). GII.4 Sydney was the most common variant (47%; 1912/4113), but new GII.4 variants/clusters emerged regionally, with GII.4 San Francisco, GII.4 Wichita and GII.4 Allegany more frequently detected than GII.4 Sydney in 2021-2022 in Africa, 2022-2023 in Central and South America and 2023-2024 in Central America. In 2023-2024, a dramatic rise in GII.17 detection was observed in most regions (32% of all 2024-2025 sequences). In North, Central and South America, Europe and Asia Pacific, GII.17 detection increased as GII.4 detection declined in 2024-2025. Other genotypes (GI.3, GII.1, GII.2, GII.3 and GII.6) had regional peaks, accounting for up to 37% of sequences during a specific season.

CONCLUSIONS: Our data may help guide norovirus vaccine development and provide a baseline of global norovirus strain distribution for evaluating the effectiveness of future vaccines in children. We continue to monitor the shifting distribution of norovirus genotypes through NoroSurv surveillance.