Norovirus represents one of the primary pathogens responsible for gastroenteritis on a global scale, exerting a significant impact on foodborne illnesses. In recent years, China has emerged as a region of particular significance with regard to the occurrence of norovirus outbreaks. This study presents a systematic review of norovirus outbreaks in China, offering a comprehensive overview and analysis of norovirus epidemics. A total of 680 articles reporting 798 outbreaks were included from four databases (CNKI, CHINA Wanfang, Web of Science, and PubMed). Firstly, an overall historical review of norovirus outbreaks in China over the past two decades is conducted, detailing the fluctuations in reported outbreak numbers and cases influenced by different global strains and the COVID-19 pandemic. A comparison of the changes in the scale of outbreaks (the number of cases, attack rate, duration, and reporting time), significant differences are found in the number of cases and duration of outbreaks (P<0.001). Furthermore, the epidemiological characteristics are examined from five perspectives: region, seasonality, setting, transmission, and genogroup. It was found that high-incidence regions are concentrated in the southern and eastern regions of China, with outbreaks primarily occurring in winter. Schools are identified as key outbreak setting, and foodborne transmission is the main mode of transmission. The GII genogroup is particularly prevalent, with GII.2 and GII.4 being the most dominant. Based on above findings, the article also cross-analyzes seasonal variations in different provinces and transmission modes under different settings and genogroups. In most settings, foodborne transmission is the primary mode, whereas person-to-person and waterborne transmission prevail in settings like schools and communities, respectively. The GII genogroup primarily spread through person-to-person contact, food, and aerosols caused by vomiting. In contrast, the GI genogroup and I/II mixed genogroups mainly spread through water and food.

A significant foodborne pathogen that causes acute gastroenteritis worldwide is sapovirus (SaV). Currently, SaV genotyping is primarily based on the VP1 gene. The single naming method based on the VP1 region can no longer suit the needs of SaV research due to the emergence of recombinant strains. Therefore, SaV nucleotide sequences with entire VP1 and NS6-7 genes sections were gathered in Genbank, and genetic distance calculations and phylogenetic analyses were carried out to investigate the double nomenclature based on SaV VP1 and NS6-7 genes. They can be further subdivided into genotypes and various genogroups based on the genetic diversity of the entire VP1 region, and 12 genogroups and 30 genotypes were found, including tentative genotypes and genogroups. The work is noteworthy for having discovered a novel genogroup, GNA1. There was an interesting discovery of a class of sequences known as bat-related sequences. The genetic distance between these sequences approached the inter-genogroup genetic distance, which in this study was classified as the bat genogroup. Thirty significant reference sequences are proposed based on the VP1 genotypes. Phylogenetically, twelve P (polymerase)-groups and 29 P-types (Including tentative genotypes and genogroup) were identified based on the genetic diversity of nucleotide sequences in the entire NS6-7 region, and related P-type reference sequences were also suggested. Nine recombinant sequences, comprising six recombinant genotypes (GI.1[P4], GI.2[P1], GII.4[P1], GII.4[PNA1], GII.6[P2], and GV.NA1[P3]), were found as a result of the dual nomenclature of the VP1 and NS6-7 genes. Dual nomenclature based on VP1 and NS6-7 genes can effectively characterize SaV recombination.