Incidence of human sapovirus outbreaks in Beijing, China, 2014-2021: predominance of genotypes GII.3 and GI.2.

The study aimed to analyze epidemiological, clinical, and genome characteristics of acute gastroenteritis (AGE) outbreaks caused by sapovirus in Beijing. Epidemiological and clinical characteristics of sapovirus detected by RT-qPCR were collected from AGE surveillance. Descriptive statistics were used for epidemiological analysis, and both genotype identification and sequence analysis were conducted on the VP1 regions, RNA-dependent RNA polymerase regions, and whole genomes. From 2014 to 2021, sapovirus was the second most common pathogen in AGE outbreaks, causing 216 outbreaks (6.85%) with peaks in 2017, 2019, and 2021. The predominant outbreaks occurred in kindergartens (76.39%, 165) and primary schools (18.98%, 41) within urban (62.96%, 136) and suburban (35.19%, 76) by person-to-person transmission (97.73%, 172). Outbreaks in outer suburbs lasted longer duration [median 7 days, IQR: 6-8]. Comprehensive schools (21.62%, IQR: 10.00-35.00%) and kindergartens (18.18%, IQR: 13.51-22.72%) showed higher attack rates. Clinical symptoms included vomiting (97.27%, 1,462), diarrhea (18.44%, 277), fever (8.32%, 125), nausea (28.72%, 432), and abdominal pain (33.94%, 510). Vomiting prevalence was higher in children aged ≤5 years (96.94%, 983/1,014), while diarrhea prevalence was higher in those >5 years (31.29%, 153/489). Eight genotypes (GI.1-3, 5, 6; GII.1, 3, 5) were identified, and the predominant genotype changed from GII.3 (2016-2019) to GI.2 (2020-2021). Phylogenetic analysis revealed emerging clades in GII.3 and GI.2, with nucleotides and amino acids mutations confirmed by whole-genome sequencing. Therefore, sapovirus is a significant AGE pathogen in Beijing, China, warranting its inclusion in surveillance among sporadic cases and outbreaks of AGE in China with necessitating genotyping and whole-genome sequencing.