A systematic review and meta-analysis indicates a substantial burden of human noroviruses in shellfish worldwide, with GII.4 and GII.2 being the predominant genotypes

Human noroviruses (HuNoVs) have been found as the leading cause of acute gastroenteritis outbreaks in all age groups and are significantly correlated with the consumption of shellfish. In this study, the contamination of HuNoVs in shellfish was estimated through a systematic review and meta-analysis. Studies on the contamination of HuNoVs in shellfish were searched from PubMed, Web of Science, Embase, and Cochrane Library from January 2000 to August 2021. A total of 75 studies were included, and the pooled HuNoVs prevalence in shellfish was 29% (95% CI: 23-35) worldwide. As revealed by the results of the subgroup meta-analysis, the prevalence of dominant genogroup was variable, and 4% (95% CI: 3-6), 13% (95% CI: 10-17), with 7% (95% CI: 4-11) of the samples, respectively, contaminated by GI alone, GII alone, and GI&GII. The HuNoVs prevalence of shellfish in Europe, America, and Asia was 33% (95% CI: 24-43), 24% (95% CI: 7-47), and 27% (95% CI: 18-35), respectively, while only 10% (95% CI: 5-17) in Africa. Furthermore, the prevalence of HuNoVs in shellfish was the highest in spring (35%, 95% CI: 23-49) and winter (35%, 95% CI: 22-50), and the lowest in summer (11%, 95% CI: 5-18). Oysters, clams, and mussels had comparable HuNoVs prevalence of 28% (95% CI: 20-37), 27% (95% CI: 16-39) and 24% (95% CI: 17-32), respectively. The prevalence of HuNoVs in shellfish from harvest areas and markets was 30% (95% CI: 23-38) and 30% (95% CI: 19-41), respectively. The results of this study suggest a substantial burden of HuNoVs in shellfish worldwide, with GII.4 (92.86%) and GII.2 (46.43%) as the predominant genotypes. This study provides information regarding the contamination of HuNoVs in shellfish worldwide, which will contribute to the development of appropriate control measures to prevent shellfish-related HuNoVs gastroenteritis.