Emergence of GII.e as a major ORF 1 norovirus genotype and its associated ORF 2 GII.4 variant forms

The noroviruses are a major cause of outbreaks of gastroenteritis. The norovirus genotype “GII.e”, identified by ORF (Open Reading Frame) 1 nucleotide sequencing, appears to be an obligatory recombinant, in that no unique GII.e ORF 2 genotype has been identified. In 2012 GII.e norovirus became the predominant ORF 1 genotype in norovirus outbreaks in Victoria, Australia, and the current study documents changes in the ORF 1 region of GII.e norovirus since it first emerged in 2008, as well as in the ORF 2 genotypes associated with GII.e norovirus. GII.e norovirus underwent significant genetic change in ORF 1 between 2010 and 2012 and this genetic change corresponded to a significant increase in the prevalence of the virus. Nucleotide sequencing of the ORF 2 region of GII.e specimens showed that in 2008–2009, all the ORF 2 sequences corresponded to the GII.4 (2007) variant, in 2010 all the ORF 2 sequences corresponded to the GII.4 (2012-like) variant and in 2012 all the ORF 2 sequences corresponded to the GII.4 (2012) variant, the GII.4 (2012-like) variant, or the GII.4 (2009-like) variant. The evidence indicated that the development of the 2012 GII.e epidemic strains was due to evolutionary change rather than a novel recombination event. The results also support the notion that ORF 1 is critical in determining the virulence of a norovirus strain.     

Comparative analysis of South African norovirus GII.4 strains identifies minor recombinant variants

Recombination within the norovirus (NoV) GII.4 genotype is well documented as a mechanism by which novel variants evolve. Norovirus GII.4 has been the predominant NoV genotype detected in South Africa (SA) in recent years and putative NoV recombinants were previously identified in SA based on partial regions of the viral genome. The objective of this study was to determine the complete genome sequence of representative NoV GII.4 variants that have circulated in SA between 2009 and 2013 and to compare major and minor GII.4 variants based on nucleotide sequence. The complete genomes of 11/27 GII.4 strains could be amplified in three or five overlapping segments, these included major variants New_Orleans_2009 and Sydney_2012 as well as three types of minor GII.4 variants. Phylogenetic and recombination analysis identified GII.4 recombinants with breakpoints located at or near the ORF1/2 junction. Apart from recombinants already recognised as major variants (GII.P4 New_Orleans_2009/GII.4 Sydney_2012 (n = 2) and GII.Pe/GII.4 Sydney_2012 (n = 2)) four further recombinant strains were detected (GII.P4 New_Orleans_2009/GII.4 Hunter_2004 (n = 1) and GII.P4 Yerseke_2006a/GII.4 Apeldoorn_2007 (n = 3)) that were attributed to three distinct minor variants. The encoded proteins with the highest diversity were p48 (Nterm), p22, VP1 and VP2. Analysis of antigenic sites in VP1 revealed mutations at epitopes A, B, C, D and E, with epitopes A and D being most variable. The high variation at epitope D was reflected in structural differences in models of GII.4 variants in the epitope D loop region (aa 393–395). Major and minor variants could not be distinguished based on specific sequence differences. HBGA-binding studies will be necessary to assess the effect of the observed amino acid differences in the P2 domain of these GII.4 strains.     

Recombinant norovirus GII.g/GII.12 gastroenteritis in children

Recombinant GII.g/GII.12 norovirus (NoV) strains emerged in 2008 in Australia and subsequently have been associated with gastroenteritis outbreaks worldwide. In the winter season 2009-2010 GII.12 strains caused 16% of the NoV outbreaks in the United States. During 2009-2010 we also identified GII.g/GII.12 strains during surveillance of sporadic cases of gastroenteritis in Italian children. Severity scores were calculated for the GII.g/GII.12 NoV infections using the Vesikari scale and in two out of three paediatric cases they exceeded the median value calculated for concomitant GII.4 infections. Upon sequence analysis, the Italian strains were found to be recombinant viruses and displayed different patterns of nucleotide polymorphisms. Phylodynamic analysis with other GII.g/GII.12 recombinants showed a high rate of evolution, comparable to the rates observed for GII.4 viruses. The mechanisms leading to worldwide emergence of GII.12 NoV strains in 2008-2010 are not clear. Monitoring of GII.12 NoV circulation is necessary to understand these mechanisms of evolution.     

Immunogenicity and specificity of norovirus Consensus GII.4 virus-like particles in monovalent and bivalent vaccine formulations

Noroviruses, a major cause of acute gastroenteritis worldwide, present antigenic diversity that must be considered for the development of an effective vaccine. In this study, we explored approaches to increase the broad reactivity of virus-like particle (VLP) norovirus vaccine candidates. The immunogenicity of a GII.4 "Consensus" VLP that was engineered from sequences of three genetically distinct naturally occurring GII.4 strains was examined for its ability to induce cross-reactive immune responses against different clusters of GII.4 noroviruses. Rabbits immunized with GII.4 Consensus VLPs developed high serum antibody titers against VLPs derived from a number of distinct wild-type GII.4 viruses, including some that had been circulating over 30 years ago. Because the sera exhibited low cross-reactivity with antigenically distinct GI norovirus strains, we investigated the serum antibody response to a bivalent vaccine formulation containing GI.1 (Norwalk virus) and GII.4 Consensus VLPs that was administered to animals under varying conditions. In these studies, the highest homologous and heterologous antibody titers to the bivalent vaccine were elicited following immunization of animals by the intramuscular route using Alhydrogel (Al(OH)(3)) as adjuvant. Our data indicate that the use of both genetically engineered norovirus VLPs that incorporate relevant epitopes from multiple strains and multivalent vaccine formulations increase the breadth of the immune response to diverse variants within a genotype and, thus, prove helpful in the rational design of VLP-based vaccines against human noroviruses.     

Genome characterization and temporal evolution analysis of a non-epidemic norovirus variant GII.8

Noroviruses are the primary cause of non-bacterial acute gastroenteritis worldwide, and GII.8 belongs to a non-epidemic genotype with a limited understanding currently. In this study, we assembled the first GII.8 norovirus genome from China and clarified the temporal evolutionary process of this non-epidemic variant. Using the “4+1+1” application strategy with newly designed primer sets, the genome of one GII.8 strain GZ2017-L601 from China was firstly sequenced that comprised 7476 nucleotides. The homology of the new genome and the previous only GII.8 genome reached 93.8% identity at the nucleotide level, but only 10, 6, 7 amino acid mutations occurred in three ORFs. When compared the new strain with other GII reference strains, p22 and P2 were calculated as the variable encoding regions, and NTPase, VPg, 3CL, RdRp and S were shown as the conserved ones. We then reconstructed the evolutionary process of the GII.8 genotype using other available sequences in GenBank. Based on the partial N/C region, all GII.8 strains could be subdivided chronologically into four clusters, which spans 1967–1994, 1997–2005, 2003–2009, and 2007–2017, respectively. Moreover, differences of capsid P proteins between GII.8 strains and the epidemic GII.4 strain VA387 were also compared. There existed 147/310 distinct amino acid sites in the alignment, including two insertion and three deletion mutations. Distribution of antigen epitopes of two GII.8 variants was comparable, but the numbers of antigenic sites of GII.8 strains were less than that of VA387. In summary, the first GII.8 genome from China was assembled and extensively characterized, and a time-order evolutionary process of this genotype was identified with a static pattern of antigenic variations.     

Pediatric norovirus GII.4 infections in Nicaragua, 1999–2015

ObjectivesInvestigate clinical and epidemiological factors of pediatric GII.4 norovirus infections in children with acute gastroenteritis (AGE) in Nicaragua between 1999 and 2015.MethodsWe retrospectively analyzed laboratory and epidemiologic data from 1,790 children ≤ 7 years with AGE from 6 hospitals in Nicaragua (n = 538), and 3 community clinics (n = 919) and households (n = 333) in León, between 1999 and 2015. Moreover, asymptomatic children from community clinics (n = 162) and households (n = 105) were enrolled. Norovirus was detected by real-time PCR and genotyped by sequencing the N-terminal and shell region of the capsid gene.ResultsNorovirus was found in 19% (n = 338) and 12% (n = 32) of children with and without AGE, respectively. In total, 20 genotypes including a tentatively new genotype were detected. Among children with AGE, the most common genotypes were GII.4 (53%), GII.14 (7%), GII.3 (6%) and GI.3 (6%). In contrast, only one (1.4%) GII.4 was found in asymptomatic children. The prevalence of GII.4 infections was significantly higher in children between 7 and 12 months of age. The prevalence of GII.4 was lowest in households (38%), followed by community clinics (50%) and hospitals (75%). Several different GII.4 variants were detected and their emergence followed the global temporal trend.ConclusionsOverall our study found the predominance of pediatric GII.4 norovirus infections in Nicaragua mostly occurring in children between 7 and 12 months of age, implicating GII.4 as the main norovirus vaccine target.     

Complete nucleotide sequence analysis of the norovirus GII.17: A newly emerging and dominant variant in China, 2015

Norovirus is an important pathogen which accounts for majority of the viral related acute gastroenteritis. Recently, a variant of genotype GII.17 was reported to be predominant over GII.4 and accounted for several acute gastroenteritis outbreaks in Asia. In the current study, the full genome of a norovirus strain ZHITHC-12 isolated during this outbreak period in China was identified and characterized. The viral genome was 7557 nucleotides in length and a phylogenetic analysis based on full length genome sequences indicated that ZHITHC-12 belonged to GII.17 genotype. A further phylogenetic analysis based on all available polymerase and capsid sequences showed that ZHITHC-12 was in Cluster III on both phylogenetic trees and grouped with other strains also isolated during 2013 to 2015. Moreover, homology modeling analysis based on GII norovirus capsid 5BSX template revealed that substitutions, mutations, and more importantly, deletions and insertions, occurred at or near the putative epitopes and histo-blood group antigen (HBGA) binding sites in its protruding P2 domain, which might confer new antigenic or biological properties for this novel variant. In summary, the first full genome and capsid protein structure of a novel norovirus GII.17 variant isolated in China was extensively characterized. The data would be helpful not only for the epidemiology study, but also for the diagnostic tool development and effective vaccine design in the future.     

Norovirus GII.4 and GII.7 capsid sequences undergo positive selection in chronically infected patients

Norovirus has become an important cause for infectious gastroenteritis. Particularly genotype II.4 (GII.4) has been shown to spread rapidly and causes worldwide pandemics. Emerging new strains evade population immunity and lead to high norovirus prevalence. Chronic infections have been described recently and will become more prevalent with increasing numbers of immunocompromized patients. Here, we studied norovirus evolution in three chronically infected patients, two genotypes II.4 and one II.7. A 719 and 757 nt region was analyzed for GII.4 and GII.7, respectively. This covers the entire hypervariable P2 domain of the VP1 capsid gene. Genetic variability at given and between different time points was assessed. Evolutionary adaptation was analyzed by Bayesian sampling of genealogies. This analysis clearly demonstrated positive selection rather than incidental drift for all three strains. The GII.7 and one GII.4 strain accumulated on average 5-9 mutations per 100 days, most of them non-synonymous. This is a much higher evolutionary rate than observed for noroviruses on a global level. Our data demonstrate that norovirus quasispecies are positively selected in chronically infected patients. The numbers of intraindividual amino acid mutations acquired in the capsid gene are similar to those separating consecutive GII.4 epidemic strains. Evolution in a given, chronically infected individual may thus generate novel genotypes at risk to expedite global evolution particularly for slowly evolving genotypes, as GII.7.     

重组GII型诺如病毒长沙株全基因组序列的测定与分析

目的 对2016年长沙地区一起由GII型诺如病毒引起的急性胃肠炎暴发疫情致病原进行全基因组序列测定,掌握其基因类型、分子进化特征和抗原重组情况。方法 提取疫情中患者粪便标本的总RNA,反转录成cDNA,PCR扩增病毒全基因组并采用Sanger法测序,比对拼接后获得病毒全基因组序列;通过BLAST比对和诺如病毒在线分型工具(typing online tool)确定其基因型别;从GenBank中下载GII型诺如病毒参考序列,采用DNA Star软件进行序列多序列比对和同源性分析,绘制系统遗传进化树,基因重组特征分析采用SimPlot软件。结果 通过一代测序获得病毒基因组序列长7491bp,有3个开放阅读框(ORF),长度分别为5100bp,1647bp,765bp。多序列比对和同源分析发现ORF1区与GII.P12型代表株同源性最高,VP1区则与GII.3型同源性最高;因此,将该毒株命名为Hu/GII.P12-GII.3/CS02/2016 /CHN。分子遗传进化分析显示其与中国其他地区如北京、上海、广东等地流行的GII.P12-GII.3重组型诺如病毒亲缘关系最为接近。抗原重组分析发现Hu/GII.P12-GII.3/CS02/2016 /CHN长沙株重组位点在5080bp,为ORF1与 ORF2重叠区的起点。结论 除了GII.P16-GII.2重组诺如病毒的广泛流行外,长沙地区仍存在GII.P12/GII.3重组诺如病毒的散发流行,需加其强监测。     

Molecular epidemiology of norovirus associated with gastroenteritis and emergence of norovirus GII.4 variant 2012 in Japanese pediatric patients

In late 2012, an outbreak of acute gastroenteritis due to norovirus variant Sydney_2012 occurred and have been reported from many counties. In this study, we described surveillance study of the incidence of norovirus infections among Japanese pediatric patients in association with gastroenteritis and investigated the antigenic change of the new variant Sydney_2012 circulated in Japanese populations. A total of 2381 fecal specimens collected from children with acute gastroenteritis in Hokkaido, Tokyo, Shizuoka, Kyoto, Osaka, and Saga from 2009 to 2013 were examined for norovirus and further analyzed molecularly. A high proportion (39.3%) of norovirus positive samples and several genotypes were detected. Norovirus GII.4 dominated over other genotypes (71.4%). The Den_Haag_2006b (43.2%) was detected as the predominant variant and co-circulated with New_Orleans_2009 (17.8%) until March 2012. Subsequently, they were displaced by Sydney_2012. The Sydney_2012 variant has been responsible for the majority of norovirus infections in 2012–2013 (85.7%). Although Sydney_2012 variant has a common ancestor with New_Orleans_2009 variant, analysis of P2 sub-domain showed a high level of diversity in comparison with other variants in four amino acid changes at the antigenic sites. The change in particular residue 393 of new variant may affect HBGA recognition. Analysis of noroviruses circulating in the past 4 years revealed a change of predominant variant of norovirus GII.4 in each epidemic season. The change of amino acid in putative epitopes may have led the virus escape from the existing herd immunity and explain the increase of new variant outbreaks.     

Efficacy of an intramuscular bivalent norovirus GI.1/GII.4 virus-like particle vaccine candidate in healthy US adults

BackgroundWe performed this first-in-human efficacy trial of Takeda’s bivalent norovirus vaccine candidate (TAK-214) against moderate or severe acute gastroenteritis (AGE) in healthy adults.MethodsThis double-blind, randomized, placebo-controlled phase 2b trial was conducted over two winter seasons in 18–49 year-old US Navy recruits. Participants were randomized (1:1) to receive intramuscular injections of saline placebo (N = 2,357) or TAK-214 [15 μg GI.1 and 50 μg GII.4c VLPs, 0.5 mg Al(OH)₃] (N = 2,355), and monitored for 45 days post-vaccination for AGE. Norovirus genotypes were identified by RT-PCR and sequencing of stool/vomitus samples. Sera from AGE cases were used to assess immune responses as genotype-specific histo-blood group antigen (HBGA)-blocking antibodies.FindingsWith low rates of homotypic norovirus AGE detected the statistical analysis was proactively modified to account for AGE due to any norovirus genotype. Of the 48 norovirus AGE cases of “any severity”, 29 in placebo and 19 in vaccinees, causative genotypes were GI.1 (n = 1), G1.7a (n = 1), GII.2 (n = 39) and GII.4 (n = 7). Applying predefined definitions of moderate or severe AGE gave 26 vs. 10 cases due to any norovirus genotype in placebo vs. vaccine groups, a vaccine efficacy (VE) of 61.8% (95.01% CI, 20.8 to 81.6; p = 0.0097). Five vs. one moderate or severe cases due to vaccine GI.1/GII.4 homotypic genotypes in placebo vs. vaccine arms gave a primary endpoint vaccine efficacy of 80.0% (99.99% CI, −1318.1 to 99.7; p = 0.142). Levels of GI.1 and GII.4 HBGA-blocking antibodies were increased in vaccinees and in some placebo AGE cases infected with GII.2, indicating cross-reactivity in the immune responses to different genotypes.InterpretationDespite limited cases of homotypic norovirus AGE meaning the primary endpoint was not fully evaluable, we showed TAK-214 provided statistically significant efficacy against “any moderate/severe norovirus AGE” principally caused by the heterotypic GII.2 genotype, demonstrating induction of cross-genotype protection.     

Epidemic viral gastroenteritis in Queensland coincides with the emergence of a new norovirus variant

Norovirus infections cause widespread morbidity and have significant economic impact on the community. An increase in outbreaks of norovirus gastroenteritis in hospitals, nursing homes and in the community was observed in Queensland in 2004. Molecular analysis of positive samples indicated the emergence of a single strain of norovirus. A 252 nucleotide sequence from the polymerase region (POL) was compared to sequences of the new variant genotype GII.4 that has caused epidemics in the Northern Hemisphere in 2002 and 2003. Sequence analysis indicated greater than 95 per cent similarity in the POL between the Queensland strain and the Northern Hemisphere 2002/3 GII.4 variant. Phylogenetic analysis revealed that the Queensland strain forms a branch within the GII.4 genotype separate from the 2002 variant from Europe and North America. Although norovirus genotype GII.4 had circulated in Queensland in the past, the 2004 strain was characterised specifically by three nucleotides not present in any other sequences held in our database covering the years 2002-June 2004.     

Detection of novel GII.17 norovirus in Argentina, 2015

During the winter of 2014–2015 a novel GII.17 norovirus strain emerged as a cause of large gastroenteritis outbreaks in Asia; displacing the long-term predominant strain, GII.4. Although sporadically detected, the emerging GII.17 virus was described in North America and Europe. In this study, we describe the presence of this novel strain in Argentina (South America), and provide new information on the genetic diversity of GII.17 noroviruses.Ten stool samples from individuals (1–88 years old; median: 5 years old) experiencing gastroenteritis symptoms from San Martín de los Andes, Argentina were tested for Norovirus using RT-PCR. Subsequently, Norovirus positive samples were analyzed by sequencing. Norovirus was found in four out of 10 samples received. Partial sequencing of the ORF2 was available for 3/4 samples: two samples belonged to genotype GII.4 and one to genotype GII.17 (Arg13099). Sequence analyses of the VP1 encoding region revealed that the GII.17 Argentinean strain presented characteristics from both, the new (cluster C), and older (cluster A and B) GII.17 strains. Phylogenetic and sequence analyses of the RdRp region showed that this strain was closely related to strains from genotypes GII.P3, GII.P13 and GII.P17; however, did not cluster within any of them.This study represents the first report of this emergent strain in South America, and presents further evidence of the genetic plasticity of the GII.17.     

Occurrence of Norovirus GII.4 Sydney Variant-related Outbreaks in Korea

Human noroviruses are major causative agents of food and waterborne outbreaks of nonbacterial acute gastroenteritis. In this study, we report the epidemiological features of three outbreak cases of norovirus in Korea, and we describe the clinical symptoms and distribution of the causative genotypes. The incidence rates of the three outbreaks were 16.24% (326/2,007), 4.1% (27/656), and 16.8% (36/214), respectively. The patients in these three outbreaks were affected by acute gastroenteritis. These schools were provided unheated food from the same manufacturing company. Two genotypes (GII.3 and GII.4) of the norovirus were detected in these cases. Among them, major causative strains of GII.4 (Hu-jeju-47-2007KR-like) were identified in patients, food handlers, and groundwater from the manufacturing company of the unheated food. In the GII.4 (Hu-jeju-47-2007KR-like) strain of the norovirus, the nucleotide sequences were identical and identified as the GII.4 Sydney variant. Our data suggests that the combined epidemiological and laboratory results were closely related, and the causative pathogen was the GII.4 Sydney variant strain from contaminated groundwater.     

Emergence of norovirus GII.2 and its novel recombination during the gastroenteritis outbreak in Japanese children in mid-2016

In mid-2016, norovirus GII.2 emerged as a major cause of gastroenteritis outbreak in Japan with overall detection rate of 56.3% of norovirus cases. The differences in ORF1 and ORF2 of some norovirus GII were observed. Inter-subtype recombinants GII.Pe/GII.2, GII.P16/GII.2 and GII.P17/GII.2 were detected. Three amino acid substitutions were noted at P2 antigenic site of GII.P16/GII.2 recombinants. Furthermore, this study revealed that the current immunochromatographic kit available in Japan could be used effectively for the detection of recent GII.2 genotype.     

Characterization of novel intragenotype recombination events among norovirus pandemic GII.4 variants

Recently, there has been an increase in the number of children hospitalized due to norovirus infection in Brazil. This is due both to the occurrence of more severe norovirus-related gastroenteritis cases after the introduction of the rotavirus vaccine and an increase in the tools for the detection of the disease. This pathogen is transmitted by the fecal-oral route, and the illness is characterized by diarrhea, vomiting, nausea and abdominal cramps. The genome of the virus is organized into three open reading frames showing strong mutation rates. Additionally, homologous recombination events, which can increase the virulence of the virus and lead to genotyping mistakes in molecular epidemiological studies, frequently occur. The purpose of this study was to describe two recombination events among different GII.4 variants that infected children who were hospitalized for severe acute gastroenteritis during distinct periods of time in Belém, Brazil. The recombination among the variants US95_96/Kaiso_2003 and Den Haag_2006b/Yerseke_2006a were observed in May 2003 and February 2009, respectively. In both cases, the association between the dominant variant at that point in time and another that was circulating at a low frequency in the population of Belém was demonstrated. Interestingly, the position of the breakpoint of the recombination event in the genome was the polymerase gene and was located at the nucleotide positions 4.834 and 5.002, which is an unusual location for the occurrence of recombination as other studies have previously reported the junction region as a breakpoint. In this study, both recombinant variant strains were related to severe cases of diarrhea that lead to hospitalization, demonstrating the viral evolution of GII.4 in response to selective pressures, which ultimately lead to the emergence of novel viral types in the pediatric population. The cases discussed here reinforce the need for continuous norovirus surveillance. To our knowledge, these two GII.4 variant recombinations have not yet been previously described.     

Molecular characterization of new emerging GII.17 norovirus strains from South China

Noroviruses are still the primary cause of non-bacterial acute gastroenteritis worldwide. Recently, a novel GII.17 norovirus variant emerged and caused an infection peak in the cold season of 2014/2015 in some Asian countries, including China. In this study, in order to understand the evolutionary advantage of the novel variant, complete genomic sequences of GII.17 NoV strains from South China were comprehensively analyzed. Pairwise alignments of new GII.17 genomes with representative sequences of each GII genotype were performed. Inconsistent homology was observed between different protein-encoding regions, of which VPg (NS5) and P2 were found to be the most conserved and variable ones, respectively. The differences between new sequences and other reported GII.17 genomes were also compared, and 84 mismatched nucleotides were found, resulting in 15 amino acid changes. Then, all capsid sequences of different GII.17 NoV variants were collected for multiple alignments, and a total of 87 spots were identified during their evolution process. Homology modeling of capsid proteins of four GII.17 variants was carried out based on comparison with GII.4 VA387 strain, and structural differences were mainly embodied in five extended loops. Furthermore, positions of potential conformational epitope regions of new GII.17 variants were found more similar or adjacent to those of GII.4 rather than those of the former GII.17 variants. In summary, nine GII.17 strains from South China were extensively characterized based on their complete genomes, and a different distribution pattern of epitope residues was predicted on the new GII.17 variant capsid from that of the former ones.     

长沙地区诺如病毒基因型分析

目的确定长沙地区引起急性胃肠炎诺如病毒的类型。方法从128例腹泻患者粪便中,提取RNA。将RNA进行逆转录、扩增、测序,并通过构建基因进化树进行分析导致长沙地区患者感染的诺如病毒的主要种类。结果63个样品中含有诺如病毒,分别为GII-3、GII-4、GII-12三种类型,其中GII-4为主要病原体。结论在长沙地区,诺如病毒GII-4是引起病毒性胃肠炎的的主要致病株。GII-4基因进化快速,已成为全球范围内导致急性胃肠炎的最常见病毒株。     

Genome characterization of a GII.6 norovirus strain identified in China

Noroviruses (NoVs) are the primary cause of non-bacterial acute gastroenteritis worldwide. Most NoV infections are caused by GII.4, but GII.6 is also an important genotype with a long-term persistence in human populations. In this study, the complete genome sequence of a NoV strain GZ2010-L96 isolated in China was identified and analyzed phylogenetically. The viral genome comprised 7550 nucleotides, and its phylogenetic analysis revealed that the strain belonged to GII.6 genotype. All reported GII.6 NoV capsid protein sequences were also collected for comparative analysis, and GZ2010-L96 was clustered into GII.6-b with other 8 strains. Meanwhile, it was found that 53 spots on viral capsid showed subcluster specificity according to multiple alignments. Moreover, homologous modeling of GZ2010-L96 based on comparison with GII.4 VA387 strain showed a different antigen distribution pattern. In summary, the genome of the GII.6 strain GZ2010-L96 detected in China was extensively characterized, and phylogenetic analyses of GII.6 NoVs based on the capsid proteins may reveal a different evolution process from the predominant genotype GII.4.     

A decade of norovirus genetic diversity in Belgium

Outbreaks of norovirus-associated gastroenteritis occur during all seasons and in various locations, and are recognized as one of the most common causes of nonbacterial food-borne infections. The molecular epidemiology of norovirus infections has not been well characterized in Belgium. To study the incidence of norovirus infections and the nature of the circulating genotypes, 3080 specimens were collected from patients with acute gastroenteritis between 2004 and 2014. Norovirus was detected with RT-PCR in 554 samples (18%). The circulating strains were genotyped based on the variability in the 5′ end of the capsid gene (region C). The GII.4 genotype, which is detected predominantly worldwide, was also the most prevalent genotype in our study (87%). This study shows a high frequency and genetic diversity of norovirus in patients with acute gastroenteritis in health care facilities in Flanders, Belgium.