Altered patterns of norovirus GII.b recombinant forms in gastroenteritis outbreaks in victoria, Australia, 2002-2005 compared to 2006-2011

Genotyping and traceability analysis of norovirus in Yantai between 2017 and 2019

To investigate the diversity and evolution of noroviruses in Yantai in recent years, this study focused on the coat protein regions of norovirus-positive samples with nucleic acid detection (cycle threshold) values below 30 between 2017 and 2019. A total of 81 sequences were obtained for genotyping. Initially, a high-throughput sequencing approach was established to perform the whole-genome sequencing of multiple typical diarrheal strains. Using bioinformatics software such as BEAST, recombinant variant analysis was performed for each genotype of the norovirus strains, and genetic evolutionary analysis was conducted for the dominant strain GII.4, as well as the rare variant GII.21. The results showed that there were multiple genotypes such as GI.3, GI.6, GI.7, GII.1, GII.2, GII.3, GII.4, GII.6, GII.13, GII.17, GII.21, and GIX.1 in the positive samples of norovirus from 2017 to 2019. GII.4 is characterized by diverse genotypes, with new changes in antigenic epitopes occurring during the course of the epidemic. This may have led to the emergence of a new pandemic. This suggests a need to strengthen surveillance. The results of this study suggest that attention should be paid to the predominant genotypes prevalent in neighboring countries and regions, and the safety supervision of imported food should be strengthened to aid in the prevention and control of related viruses.

Norovirus recombinants: recurrent in the field, recalcitrant in the lab - a scoping review of recombination and recombinant types of noroviruses

Noroviruses are recognized as the major global cause of sporadic and epidemic non-bacterial gastroenteritis in humans. Molecular mechanisms driving norovirus evolution are the accumulation of point mutations and recombination. Intragenotypic recombination has long been postulated to be a driving force of GII.4 noroviruses, the predominant genotype circulating in humans for over two decades. Increasingly, emergence and re-emergence of different intragenotype recombinants have been reported. The number and types of norovirus recombinants remained undefined until the 2007 Journal of General Virology research article 'Norovirus recombination' reported an assembly of 20 hitherto unclassified intergenotypic norovirus recombinant types. In the intervening decade, a host of novel recombinants has been analysed. New recombination breakpoints have been described, in vitro and in vivo studies supplement in silico analyses, and advances have been made in analysing factors driving norovirus recombination. This work presents a timely overview of these data and focuses on important aspects of norovirus recombination and its role in norovirus molecular evolution. An overview of intergenogroup, intergenotype, intragenotype and 'obligatory' norovirus recombinants as detected via in silico methods in the field is provided, enlarging the scope of intergenotypic recombinant types to 80 in total, and notably including three intergenogroup recombinants. A recap of advances made studying norovirus recombination in the laboratory is given. Putative drivers and constraints of norovirus recombination are discussed and the potential link between recombination and norovirus zoonosis risk is examined.

Full-genome sequence analysis of an uncommon norovirus genotype, GII.21, from South Korea

Noroviruses (NoVs) are major causal agents of acute gastroenteritis in humans. NoV GII.4 is the predominant genotype globally. However, uncommon and minor types of NoVs are consistently detected and some have been shown to dominate over GII.4. Therefore, the prevalence of dominant and uncommon NoVs makes the identification of these viruses important for the prediction and prevention of pandemics. In this study, the full-genome sequence of a NoV (strain JW) detected in Korea was extensively characterized. The full-length genome was 7510 nucleotides long, and phylogenetic analysis based on the whole-genome sequences, including open reading frame (ORF)1, ORF2, and ORF3, indicated that it belonged to the GII.21 genotype. Strain JW showed maximum identity with strain YO284; however, comparison of the amino acid sequence of ORF2, which functions as an antigen, showed substitutions in several amino acids. GII.21 is not a prevalent epidemiological agent of acute gastroenteritis in humans, but it is consistently found in gastroenteritis patients from several countries. The present study provides the first full-genome sequence analysis of NoV GII.21 isolated from a patient in Korea. Our findings provide not only valuable genome information but also data for epidemiology studies, epidemic prevention, and vaccine development strategies.

Norovirus genotype diversity in community-based sporadic gastroenteritis incidents: a five-year study

Although norovirus is a known cause of sporadic gastroenteritis, the incidence and genotypes of norovirus associated with sporadic community-based gastroenteritis are poorly understood. The current study examined this issue by using material from alleged food poisoning incidents in the state of Victoria, Australia, for the period 2008-2012. Norovirus was identified, by either ORF (open reading frame) 1 or ORF 2 RT-PCR methodology, in 159 of 379 (42.0%) sporadic gastroenteritis incidents, thereby showing that norovirus was an important cause of sporadic gastroenteritis. The number of sporadic norovirus incidents did not vary significantly from year to year, indicating that the pool of circulating norovirus remained constant. Norovirus ORF 1 genotypes identified included GI.1, GI.2, GI.3, GI.4, GI.b, GI.d, GII.2, GII.4 (including variants 2006a, 2006b, 2007, and 2009), GII.16, GII.22, GII.b, GII.e, and GII.g. Norovirus ORF 2 genotypes identified included GI.1, GI.2, GI.3, GI.4, GI.6, GII.2, GII.3, GII.4 (variants 2006b, 2009, 2009-like, 2012, and "unknown"), GII.6, GII.7, GII.9, GII.12, and GII.13. Five ORF 1/ORF 2 norovirus recombinant forms were confirmed: GII.b/GII.3, GII.e/GII.4 (2012), GII.e/GII.4 (unknown), GII.g/GII.12 and GII.16/GII.2. Although the incidence of ORF 2 GI.3 was significantly higher in children than in adults, this was not the case for other major ORF 2 genotypes (GII.2, GII.4, and GII.6) which occurred equally in all age groups. The findings demonstrate the importance and diverse nature of norovirus in sporadic community-based gastroenteritis incidents and indicate that the development of successful vaccine strategies may be difficult.