Variation of human norovirus GII genotypes detected in Ibaraki, Japan, during 2012–2018

Abstract

Background Human norovirus (HuNoV) is the major cause of viral acute gastroenteritis for all age groups in various countries. HuNoV GII in particular accounted for the majority of norovirus outbreaks, among which GII.4 caused repeated outbreaks for a long time. Besides GII.4, other norovirus genotypes, GII.2, GII.6, and GII.17, have also been prevalent in various contexts in recent years, but few detailed epidemiological studies of them have been performed and are poorly understood. We thus conducted an epidemiological analysis of HuNoV GII in Ibaraki Prefecture, Japan, by performing surveillance in the six seasons from September 2012 to August 2018. Results HuNoV GI occurred almost sporadically for all genotypes; however, each genotype of GII exhibited its typical epidemiological characteristics. Although the number of outbreaks of GII.4 decreased season by season, it reemerged in 2017/2018 season. The timing of the epidemic peak in terms of number of cases for GII.17 differed from that for the other genotypes. The patients age with GII.2 and GII.6 were younger and outbreak of GII.17 occurred frequently as food poisoning. Namely, the primarily infected outbreak group differed for each genotype of HuNoV GII. Moreover, the viral load of patients differed according to the genotype. Conclusions Various HuNoV genotypes including GII.2, GII.4, GII.6, and GII.17 were shown to be associated with various types of outbreak sites (at childcare and educational facilities, involving cases of food poisoning, and at elderly nursing homes) in this study. These genotypes emerged in recent years, and their prevalence patterns differed from each other. Moreover, differences in outbreak sites and viral load of patients among the genotypes were identified.

Molecular Characterization of Norovirus Strains Isolated from Older Children and Adults in Impoverished Communities of Vhembe District, South Africa

“…In the phylogenetic tree, GII.1 clustered together with the genotypes from environmental samples ( Figure 2 ). This could be supported by Motoya et al's [ 56 ] speculation that both GI and GII strains can be detected in environmental samples.…”

“…is could be supported by Motoya et al's [56] speculation that both GI and GII strains can be detected in environmental samples. (iv) GII.2 genotype reported in this study has been previously reported more common in hospitalised older children than in younger children [31,57,58].…”

Molecular epidemiology and genetic diversity of norovirus infection in children hospitalized with acute gastroenteritis in East Java, Indonesia in 2015–2019

“…Although noroviruses are antigenically and genetically diverse, a single genotype, i.e., GII.4, has been the predominant genotype globally. This genotype has been associated with not only sporadic gastroenteritis in children but also outbreaks in adults in various countries (Motoya et al, 2019;Wu et al, 2015;Polkowska et al, 2014;Medici et al, 2009). It was reported that the norovirus prevalence among hospitalized children was 18.5%, and that the most prevalent genotype in 2015 in Yogyakarta/West Nusa Tenggara, Indonesia was GII.4 Sydney[P31] (56%) (Nirwati et al, 2019).…”

Comparison of a one-step real-time RT-PCR and a nested real-time RT-PCR for a genogroup II norovirus reveals differences in sensitivity depending upon assay design and visualization

“…Both assays have been shown to have broad specificity across genogroup II. However, genogroup II.2 (GII.2) has recently been reemerging as the cause of outbreaks in Japan and China [ 13 , 14 ]. For this purpose, a GII.2 strain, Snow Mountain, was selected as the target norovirus strain.…”