Virus Genotype Distribution and Virus Burden in Children and Adults Hospitalized for Norovirus Gastroenteritis, 2012-2014, Hong Kong

Molecular epidemiology and genetic diversity of norovirus among hospitalized patients with acute gastroenteritis in Shandong, China, 2016-2018

Norovirus (NoV) infection is a leading cause of acute gastroenteritis (AGE) for people of all ages. Here, we reported the molecular epidemiology and genetic diversity of NoVs among hospitalized patients with AGE between 2016 and 2018 in Shandong Province, China. Two thousand sixty-nine AGE patients from sentinel hospitals were enrolled. The stool samples were collected and tested for NoVs by real-time RT-PCR. The RNA-dependent RNA polymerase (RdRp) and capsid gene of 163 strains were amplified and sequenced for genotyping. Phylogenetic analyses and genomic characterization were conducted with the VP1 and RdRp region of the full genome sequences. Four hundred seventy two (21.76%) samples were NoV-positive. The positive rate in 2016 was higher than those of 2017 and 2018. We observed diverse NoV genotypes. GII.2[P16] emerged in January 2017 and became the dominant genotype between May and June 2017. Phylogenetic analyses showed that our GII.2[P16] genomes clustered in the SC1 in VP1 region, while they belonged to the Emerging GⅡ.P16 (2015-2017) clade in RdRp region. Our GⅡ.4 strains displayed two amino acid mutations, positions R297H and D372N, in epitope A of the VP1 region. Our study highlighted that NoV is an important pathogen of viral AGE in Shandong and, therefore, it is necessary to strengthen its surveillance.

Profiling of humoral immune responses to norovirus in children across Europe

Norovirus is a leading cause of epidemic acute gastroenteritis. More than 30 genotypes circulate in humans, some are common, and others are only sporadically detected. Here, we investigated whether serology can be used to determine which genotypes infect children. We established a multiplex protein microarray with structural and non-structural norovirus antigens that allowed simultaneous antibody testing against 30 human GI and GII genotypes. Antibody responses of sera obtained from 287 children aged < 1 month to 5.5 years were profiled. Most specific IgG and IgA responses were directed against the GII.2, GII.3, GII.4, and GII.6 capsid genotypes. While we detected antibody responses against rare genotypes, we found no evidence for wide circulation. We also detected genotype-specific antibodies against the non-structural proteins p48 and p22 in sera of older children. In this study, we show the age-dependent antibody responses to a broad range of norovirus capsid and polymerase genotypes, which will aid in the development of vaccines.

Norovirus outbreaks in long-term care facilities in Catalonia from 2017 to 2018

Norovirus is the leading cause of outbreaks of acute viral gastroenteritis. We carried out this study to investigate outbreaks in long-term care facilities reported in 2017 and 2018 in Catalonia (Spain). The characteristics of the centers, exposed persons and the genogroups responsible were analyzed. Viral loads were estimated. The attack rate (AR) of the outbreaks studied, and the rate ratio (RR) and the odds ratio (OR) and their 95% confidence intervals as measures of association were calculated. The mean cycle thresholds were compared using the t-test for independent means. We included 30 outbreaks (4631 exposed people). The global AR was 25.93%. The RR of residents vs. staff was 2.28 (95% CI 2.0–2.6). The RR between AR in residents with total or severe dependence vs. residents with moderate, low or no-dependence was 1.23 (95% CI 1.05–1.45). The AR were higher in smaller centers than in larger ones (38.47% vs. 19.25% and RR 2; 95% CI 1.82–2.2). GII was responsible for 70% of outbreaks. No association was found between the genogroup and presenting symptoms (OR 0.96; 95% CI 0.41–2.26). Viral loads were higher in symptomatic than in asymptomatic patients (p = 0.001).

Identification of Human Norovirus GII.3 Blockade Antibody Epitopes

Human noroviruses are a common pathogen causing acute gastroenteritis worldwide. Among all norovirus genotypes, GII.3 is particularly prevalent in the pediatric population. Here we report the identification of two distinct blockade antibody epitopes on the GII.3 capsid. We generated a panel of monoclonal antibodies (mAbs) from mice immunized with virus-like particle (VLP) of a GII.3 cluster 3 strain. Two of these mAbs, namely 8C7 and 8D1, specifically bound the parental GII.3 VLP but not VLPs of GII.4, GII.17, or GI.1. In addition, 8C7 and 8D1 efficiently blocked GII.3 VLP binding with its ligand, histo-blood group antigens (HBGA). These data demonstrate that 8C7 and 8D1 are GII.3-specific blockade antibodies. By using a series of chimeric VLPs, we mapped the epitopes of 8C7 and 8D1 to residues 385-400 and 401-420 of the VP1 capsid protein, respectively. These two blockade antibody epitopes are highly conserved among GII.3 cluster 3 strains. Structural modeling shows that the 8C7 epitope partially overlaps with the HBGA binding site (HBS) while the 8D1 epitope is spatially adjacent to HBS. These findings may enhance our understanding of the immunology and evolution of GII.3 noroviruses.

Characteristics of GII.4 Norovirus Versus Other Genotypes in Sporadic Pediatric Infections in Davidson County, Tennessee, USA

BACKGROUND

Norovirus is a leading cause of epidemic acute gastroenteritis (AGE), with most outbreaks occurring during winter. The majority of outbreaks are caused by GII.4 noroviruses; however, data to support whether this is true for sporadic medically attended AGE are limited. Therefore, we sought to compare the clinical characteristics and seasonality of GII.4 vs non-GII.4 viruses.

METHODS

Children aged 15 days -17 years with AGE symptoms were recruited from the outpatient, emergency department, and inpatient settings at Vanderbilt Children's Hospital, Davidson County, Nashville, Tennessee, from December 2012 -November 2015. Stool specimens were tested using qRT-PCR for GI and GII noroviruses and subsequently genotyped by sequencing a partial region of the capsid gene.

RESULTS

A total of 3705 patients were enrolled, and stool specimens were collected and tested from 2885 (78%) enrollees. Overall, 636 (22%) samples were norovirus-positive, of which 567 (89%) were GII. Of the 460 (81%) genotyped GII-positive samples, 233 (51%) were typed as GII.4 and 227 (49%) as non-GII.4. Compared with children with non-GII.4 infections, children with GII.4 infections were younger, more likely to have diarrhea, and more likely to receive oral rehydration fluids. Norovirus was detected year-round and peaked during winter.

CONCLUSIONS

Approximately 40% of sporadic pediatric norovirus AGE cases were caused by GII.4 norovirus. Children infected with GII.4 had more severe symptoms that required more medical care. Seasonal variations were noticed among different genotypes. These data highlight the importance of continuous norovirus surveillance and provide important information on which strains pediatric norovirus vaccines should protect against.

Molecular epidemiology of norovirus infections in children with acute gastroenteritis in 2017-2019 in Tianjin, China

Norovirus (NoV) is the leading cause of acute gastroenteritis (AGE) worldwide. Globally, the GII.4 Sydney 2012 strain has predominated since 2012, although GII.4 variant strains have caused AGE outbreaks in China. Recent patterns of NoV genotype distributions in 6011 children with AGE in Tianjin, China were investigated. NoV was detected using real-time reverse-transcriptase polymerase chain reaction and sequencing of partial sequences of the viral capsid gene. NoV genotypes were determined, and phylogenetic analysis was conducted. Epidemiological and clinical data were compared between children infected with different NoV genotypes. NoV was detected in 27.6% of the specimens tested. GII.4 strains comprised 49.4% infections, followed by GII.3 at 39.9%. Genotypes GII.2, GII.13, GII.17, GII.1, GII.6, and GII.14 were also detected. NoV was detected during most of the year, with a peak season of cases in the winter. Diarrhea, vomiting, fever, abdominal pain, and dehydration were present in patients with NoV infection. The main genotypes were GII.4 and GII.3, with a slight increase in GII.2, beginning in March 2017. Among the GII.4 strains, GII.4 Sydney 2012 was the only epidemic strain in Tianjin. Patients with GII.4 genotypes were more likely to present with diarrhea and vomiting than those with GII.3. Children with GII. Others were prone to suffered from dehydration and abdominal pain than those with GII.3. NoV GII has become the main cause of viral AGE in Tianjin, China. The predominant genotypes of NoV were GII.4 and GII.3. Identification of emerging genotypes is crucial for the prevention and control of NoV-caused AGE.

Diagnostic Accuracy of Immunochromatographic Tests for the Detection of Norovirus in Stool Specimens: a Systematic Review and Meta-Analysis

Noroviruses are the leading cause of acute gastroenteritis in all age groups and constitute a major health and economic burden worldwide. This systematic review and meta-analysis aimed to determine the diagnostic accuracy of immunochromatographic tests (ICTs) for the detection of norovirus in stool specimens, which has not been performed previously. In this systematic review and meta-analysis (registered on PROSPERO, CRD42020186911), we searched Medline/PubMed, Embase, Cochrane Library, and Web of Science for all studies published up to 16 May 2020. The values for sensitivity, specificity, positive likelihood ratio (LR+), negative likelihood ratio (LR-), and diagnostic odds ratio (DOR) of ICTs with 95% confidence interval (CI) were pooled using a bivariate random-effects model. The summary receiver operating characteristic curve and area under the curve were used to summarize overall test accuracy. We included 43 studies describing 7,428 samples. The overall estimates of sensitivity, specificity, LR+, LR-, DOR, and accuracy of ICT for diagnosing norovirus were 0.61 (95% CI, 0.54 to 0.67), 0.97 (95% CI, 0.95 to 0.98), 17.08 (95% CI, 11.15 to 26.18), 0.40 (95% CI, 0.34 to 0.46), 53.9 (95% CI, 31.32 to 92.78), and 0.928, respectively. Significant differences in pooled sensitivities were noted between age groups and in pooled DOR and LR+ between genogroups of included samples. ICT provides low sensitivity but high specificity and accuracy for detecting norovirus. Thus, an ICT for norovirus can be a rapid and convenient way for identifying patients early; however, a negative result cannot rule out norovirus infection and should be confirmed by a reference test.

Prevalence and Evolution of Noroviruses between 1966 and 2019, Implications for Vaccine Design

Noroviruses (NoVs), a group of single-stranded RNA viruses causing epidemic acute gastroenteritis in humans, are highly diverse, consisting of multiple genogroups with >30 genotypes. Their continual evolutions make NoV vaccine design and development difficult. Here, we report a study of NoV sequences obtained from a population-based diarrhea surveillance in Zhengding County of Hebei Province spanning from 2001 to 2019 and those available in the GenBank database from 1966 to 2019. NoV genotypes and/or variants that may evade immunity were screened and identified based on primary and conformational structures for vaccine design. We selected 366, 301, 139, 74 and 495 complete VP1-coding nucleotide sequences representing the predominant genotypes of GII.4, GII.2, GII.3, GII.6 and GII.17, respectively. A total of 16 distinct GII.4 variants were identified, showing a typical linear evolutionary pattern of variant replacement, while only 1–4 variants of the other genotypes were found to co-circulate over the 40–50-year period without typical variant replacement. The vaccine strain GII.4c is close to variant Sydney_2012 (0.053) in their primary structure, but they are distinct at epitopes A and E in conformations. Our data suggested GII.4 variant Sydney_2012, GII.2 variant A, a GII.3 strain, GII.6 variants B and C and GII.17 variant D are primary candidate strains for NoV vaccine development.

Molecular epidemiology and genetic diversity of norovirus among hospitalized children with acute gastroenteritis in Tianjin, China, 2018-2020

Background

Norovirus (NoV) is a major cause of viral acute gastroenteritis (AGE) in children worldwide. Epidemiological analysis with respect to the virus strains is limited in China. This study aimed to investigate the prevalence, patterns, and molecular characteristics of NoV infection among children with AGE in China.

Methods

A total 4848 stool samples were collected from children who were admitted with AGE in Tianjin Children’s Hospital from August 2018 to July 2020. NoV was preliminarily detected using real-time reverse transcription polymerase chain reaction (RT-PCR). Partial sequences of the RNA-dependent RNA polymerase (RdRp) and capsid genes of positive samples were amplified by conventional RT-PCR and then sequenced. The NoV genotype was determined by online Norovirus Typing Tool Version 2.0, and phylogenetic analysis was conducted using MEGA 6.0.

Results

The prevalence of NoV was 26.4% (1280/4848). NoV was detected in all age groups, with the 7–12 months group having the highest detection rate (655/2014, 32.5%). NoV was detected during most part of the year with higher frequency in winter than other seasons. Based on the genetic analysis of RdRp, GII. Pe was the most predominant genotype detected at 70.7% (381/539) followed by GII.P12 at 25.4% (137/539). GII.4 was the most predominant capsid genotype detected at 65.3% (338/518) followed by GII.3 at 26.8% (139/518). Based on the genetic analysis of RdRp and capsid sequences, the strains were clustered into 10 RdRp–capsid genotypes: GII.Pe-GII.4 Sydney 2012 (65.5%), GII.P12-GII.3 (27.2%), GII.P16-GII.2 (1.8%), GII.P12-GII.2 (0.2%), GII.P17-GII.17 (1.1%), GII.Pe-GII.3 (1.8%), GII.Pe-GII.2 (1.1%), GII.Pe-GII.1 (0.4%), GII.16-GII.4 Sydney 2012 (0.7%), and GII.P7-GII.6 (0.2%). The predominant NoV genotypes changed from GII.Pe-GII.4 Sydney 2012 and GII.P12-GII.3 between August 2018 and July 2019 to GII.Pe-GII.4 Sydney 2012 and GII.P16-GII.2 between August 2019 and July 2020. The patients with GII.Pe-GII.4 Sydney 2012 genotype were more likely to suffer from vomiting symptom than those with GII.P12-GII.3.

Conclusions

NoV is an important pathogen responsible for viral AGE among children in China. GII.Pe-GII.4 Sydney 2012 and GII.P12-GII.3 were major recombinant genotypes. Knowledge of circulating genotypes and seasonal trends is of great importance for disease prevention and surveillance.

Trends in Incidence of Norovirus-associated Acute Gastroenteritis in 4 Veterans Affairs Medical Center Populations in the United States, 2011-2015

BACKGROUND

Norovirus is an important cause of epidemic acute gastroenteritis (AGE), yet the burden of endemic disease in adults has not been well documented. We estimated the prevalence and incidence of outpatient and community-acquired inpatient norovirus AGE at 4 Veterans Affairs Medical Centers (VAMC) (Atlanta, Georgia; Bronx, New York; Houston, Texas; and Los Angeles, California) and examined trends over 4 surveillance years.

METHODS

From November 2011 to September 2015, stool specimens collected within 7 days of AGE symptom onset for clinician-requested diagnostic testing were tested for norovirus, and positive samples were genotyped. Incidence was calculated by multiplying norovirus prevalence among tested specimens by AGE-coded outpatient encounters and inpatient discharges, and dividing by the number of unique patients served.

RESULTS

Of 1603 stool specimens, 6% tested were positive for norovirus; GII.4 viruses (GII.4 New Orleans [17%] and GII.4 Sydney [47%]) were the most common genotypes. Overall prevalence and outpatient and inpatient community-acquired incidence followed a seasonal pattern, with higher median rates during November-April (9.2%, 376/100 000, and 45/100 000, respectively) compared to May-October (3.0%, 131/100 000, and 13/100 000, respectively). An alternate-year pattern was also detected, with highest peak prevalence and outpatient and inpatient community-acquired norovirus incidence rates in the first and third years of surveillance (14%-25%, 349-613/100 000, and 43-46/100 000, respectively).

CONCLUSIONS

This multiyear analysis of laboratory-confirmed AGE surveillance from 4 VAMCs demonstrates dynamic intra- and interannual variability in prevalence and incidence of outpatient and inpatient community-acquired norovirus in US Veterans, highlighting the burden of norovirus disease in this adult population.

Genomic and biological characterization of a pandemic norovirus variant GII.4 Sydney 2012

Genogroup II, genotype 4 noroviruses (GII.4 NoVs) are a leading cause of epidemic and sporadic acute non-bacterial gastroenteritis worldwide. In this study, we isolated a GII.4 NoV strain (designated 2015HN08) from a kid presenting with acute gastroenteritis and determined its near-complete genome sequence. We then performed sequence analysis by comparing this strain with the prototypical GII.4 strain. Virus-like particles (VLPs) derived from the major capsid protein (VP1) were expressed by using a recombinant-baculovirus expression system, and monoclonal antibodies (mAbs) were produced to compare changes in antigenic or histo-blood group antigens (HBGAs) binding sites with the previously characterized GII.4 NoV strain (JZ403). The genome of 2015HN08 was 7559 nucleotides (nt) long, excluding the poly(A) tail. Genotyping analysis indicated that this strain was a Sydney 2012 variant. In comparison with the prototype Sydney 2012 strain, there were 74, 35, and 16 differences in nucleotide sequences in ORF1, OFR2, and OFR3, causing 7, 10, and 6 amino acid (aa) changes, respectively. Expression of VP1 led to successful assembly of VLPs, as demonstrated by electron microscopy. Screening of hybridoma cell supernatants with an in vitro VLP-HBGAs binding blockade assay led to the identification of a cell clone 3G10 that exhibited HBGA-blocking effects. This mAb also exhibited blocking effects against JZ403 strain, suggesting maintenance of the antigenic site and/or HBGAs binding sites between the two strains. In summary, we determined the near-complete genome sequence of a GII.4 Sydney 2012 variant and produced an mAb with blocking effects that might be useful in evaluating the evolution of current Sydney 2012 NoV strains.

Clinical manifestation of norovirus infection in children aged less than five years old admitted with acute diarrhea in Surabaya, Indonesia: a cross-sectional study

Background: The objective of this study was to investigate the clinical manifestation of norovirus infection between norovirus genogroup and severity of acute diarrhea in pediatric patients at the Dr. Soetomo Hospital, Surabaya, Indonesia. Methods: This cross-sectional study involved 31 participants aged 1-60 months admitted to the hospital with acute diarrhea from April 2012 to March 2013. Norovirus genogroups (GI and II) were identified from patient stool using reverse transcription polymerase chain reaction (RT-PCR). Severity was measured using the Ruuska and Vesikari scoring system. Results: In total, 94 stool samples were obtained, of which 31 (19%) were norovirus positive. Norovirus GI was found in one sample with mild diarrhea. Norovirus GII was found in 30 samples (96.8%); one sample with mild diarrhea (3.3%), 20 samples with moderate diarrhea (66.7%), and nine samples with severe diarrhea (30%). Conclusion: Norovirus GII was the most prevalent cause of acute diarrhea and 30% of the cases manifested as severe diarrhea.

Burden of Severe Norovirus Disease in Taiwan, 2003-2013

Background

Despite the increasingly recognized role of norovirus in global acute gastroenteritis (AGE), specific estimates of the associated disease burden remain sparse, primarily due to limited availability of sensitive norovirus diagnostics in the clinical setting. We sought to estimate the incidence of norovirus-associated hospitalizations by age group in Taiwan using a previously developed indirect regression method.

Methods

AGE-related hospitalizations in Taiwan were identified using International Classification of Diseases, Ninth Revision, Clinical Modification codes abstracted from a national database; population data were provided from the Department of Household Registration Affairs. Population and hospitalizations were aggregated by month and year (July 2003-June 2013) and grouped by age: <5 years, 5-19 years, 20-64 years, and ≥65 years. Monthly counts of cause-unspecified AGE hospitalizations were modeled as a function of counts of known causes, and the residuals were then analyzed to estimate norovirus-associated hospitalizations.

Results

Over the study period, an annual mean of 101400 gastroenteritis-associated hospitalizations occurred in Taiwan (44 per 10000 person-years), most of which (83%) had no specified cause. The overall estimated rate of norovirus-associated hospitalizations was 6.7 per 10000 person-years, with the highest rates in children aged <5 years (63.7/10000 person-years). Predicted norovirus peaked in 2006-2007 and 2012-2013.

Conclusions

Our study is one of the first to generate a population-based estimate of severe norovirus disease incidence in Asia, and highlights the large burden of norovirus in Taiwan, particularly in children. Predicted peak norovirus seasons coincided with the emergence of new strains and resulting pandemics, supporting the validity of the estimates.

Higher Viral Load of Emerging Norovirus GII.P16-GII.2 than Pandemic GII.4 and Epidemic GII.17, Hong Kong, China

We compared viral load of emerging recombinant norovirus GII.P16-GII.2 with those for pandemic GII.Pe-GII.4 and epidemic GII.P17-GII.17 genotypes among inpatients in Hong Kong. Viral load of GII.P16-GII.2 was higher than those for other genotypes in different age groups. GII.P16-GII.2 is as replication competent as the pandemic genotype, explaining its high transmissibility and widespread circulation.

[Molecular epidemiology of norovirus in children with acute gastroenteritis in Tianjin, China]

OBJECTIVE

To investigate the molecular epidemiological characteristics of norovirus (NoV) among children with acute gastroenteritis in Tianjin in 2017.

METHODS

A total of 758 stool specimens were collected from the children with acute gastroenteritis possibly caused by viral infection in Tianjin Children's Hospital between January and December, 2017. Quantitative real-time RT-PCR was used for primary screening of NoV, and conventional RT-PCR was used for gene amplification, sequencing and genotype identification of the VP1 region of capsid protein in positive specimens.

RESULTS

Among the 758 specimens, 241 (31.8%) were found to have GII NoV. Sequencing of the VP1 region of capsid protein in positive specimens showed that among the 241 specimens with GII NoV, 69 (28.6%) had GII.4 subtype, 51 (21.2%) had GII.3 subtype, 24 (10.0%) had GII.2 subtype, and 18 (7.5%) had other subtypes. There was a significant difference in NoV detection rate between different age groups (P=0.018), and the 1- <4 years group had the highest NoV detection rate (37.3%). There was also a significant difference in NoV detection rate across seasons (P<0.001), and there was a highest NoV detection rate in winter (48.1%). Twenty-seven children (3.6%) had co-infections with NoV and rotavirus.

CONCLUSIONS

NoV is one of the major pathogens of the children with acute gastroenteritis from Tianjin in 2017. GII genotype, especially GII.4 subtype, is the prevalent strain. NoV infection is commonly seen in children less than 4 years and reaches the peak in winter. Some children are found to have co-infections with rotavirus.

Epidemiologic and Genotypic Distribution of Noroviruses Among Children With Acute Diarrhea and Healthy Controls in a Low-income Rural Setting

Background

Noroviruses are the most common cause of epidemic and endemic acute gastroenteritis (AGE) worldwide. The burden of norovirus disease in low-income settings is poorly understood.

Methods

We tested stool samples from children less than 5 years of age with diarrhea who were admitted in a rural hospital in Bangladesh from 2010–2012 and from matched, healthy controls from the same catchment area.

Results

Norovirus was detected in 109 (18%) of 613 children with diarrhea and in 30 (15%) of 206 healthy controls. Most (n = 118; 85%) norovirus infections belonged to genogroup II (GII). Of these, GII.4 viruses were identified in 36 (33%) of the cases and in 6 (21%) of the controls. Other major genotypes included GII.3 (13%), GII.6 (11%), and GII.13 (11%) in the cases and GII.6 (17%) and GII.2 (14%) in the controls. The greatest risk of severe norovirus disease (Vesikari score ≥11) was associated with GII.4 infections. GII.4 viruses were the predominant genotype detected during the winter (55%) and rainy season (23%), while GII.3 (19%) and GII.13 (19%) viruses were the most prevalent genotypes during the summer. Vomiting was significantly associated with GII.4 infections, while longer durations of diarrhea were associated with GI.3 infections.

Conclusions

Future studies are needed to understand the high rates of virus shedding in children without AGE symptoms.

Chimeric GII.3/GII.6 norovirus capsid (VP1) proteins: characterization by electron microscopy, trypsin sensitivity and binding to histo-blood group antigens

GII.3 and GII.6 noroviruses (NoVs) are similar in several aspects, including the presence of a short sequence insertion in the P2 domain of the major capsid protein (VP1) and trypsin susceptibility of VP1-containing virus-like particles (VLPs). In this study, we generated two constructs with the S or P domains of VP1 from GII.3 and GII.6 NoV strains exchanged (GII.3S/GII.6P and GII.6S/GII.3P), and the resultant chimeric capsid proteins were expressed from recombinant baculoviruses. The assembly of VLPs was confirmed by electron microscopy, and the susceptibility of assembled VLPs to trypsin digestion was analyzed by SDS-PAGE. Salivary histo-blood group antigen (HBGA) binding and binding blockade assays were performed to determine the binding characteristics of chimeric VP1-containing VLPs with and without trypsin digestion. Our results indicated that both expressed GII.3S/GII.6P and GII.6S/GII.3P chimeric proteins successfully assembled into VLPs. Trypsin digestion of VLPs assembled from both chimeric proteins led to the generation of two fragments with molecular sizes similar to those of wild-type VP1-containing VLPs. An in vitro salivary HBGA binding assay demonstrated that VLPs assembled from both chimeric proteins exhibited enhanced binding after trypsin cleavage. An HBGA binding blockade assay indicated that the binding of GII.3S/GII.6P and GII.6S/GII.3P VLPs against salivary HBGAs could only be blocked by GII.3 and GII.6 NoV VLP-specific hyperimmune sera, respectively. For GII.6 and GII.3S/GII.6P VLPs, a difference in binding enhancement after trypsin cleavage was observed. Our results demonstrate that the S domains of GII.3 and GII.6 NoV VP1 are interchangeable and that the S domain affects the binding of the P domain to HBGAs.

Genomic characterization of GII.3 noroviruses isolated from children in Zhengzhou city, China, 2015/16

In this study, we isolated, amplified and sequenced GII.3 norovirus (NoV) strains from children admitted to a department of pediatric gastroenterology presenting with acute gastroenteritis from September 2015 to March 2016. A total of 35 stool samples were collected and eight were GII.3 NoV positive, based on sequencing. The complete genome sequences were determined for two strains while partial genome sequences, encompassing approximately 3.2 kb of the 3´end, were generated for the six other strains. Genotyping analysis of all strains indicated that they belonged to GII P12/GII.3. Phylogenetic analysis indicated that these isolated strains could be divided into two clusters. Strains in cluster IV were the most frequently isolated and exhibited less intra-cluster variation in nucleotide sequences. Our study demonstrated that the GII.P12/GII.3 recombinant strain was the dominant GII.3 NoVs in Zhengzhou city.

Increased Detection of Emergent Recombinant Norovirus GII.P16-GII.2 Strains in Young Adults, Hong Kong, China, 2016-2017

A new recombinant norovirus GII.P16-GII.2 outnumbered pandemic GII.4 as the predominant GII genotype in the winter of 2016-2017 in Hong Kong, China. Half of hospitalized case-patients were older children and adults, including 13 young adults. This emergent norovirus targets a wider age population compared with circulating pandemic GII.4 strains.

Norovirus Infection in Older Adults: Epidemiology, Risk Factors, and Opportunities for Prevention and Control

Norovirus is the leading cause of acute gastroenteritis. In older adults, it is responsible for an estimated 3.7 million illnesses; 320,000 outpatient visits; 69,000 emergency department visits; 39,000 hospitalizations; and 960 deaths annually in the United States. Older adults are particularly at risk for severe outcomes, including prolonged symptoms and death. Long-term care facilities and hospitals are the most common settings for norovirus outbreaks in developed countries. Diagnostic platforms are expanding. Several norovirus vaccines in clinical trials have the potential to reap benefits. This review summarizes current knowledge on norovirus infection in older adults.

Complete Genome Sequence of an Emergent Recombinant GII.P16-GII.2 Norovirus Strain Associated with an Epidemic Spread in the Winter of 2016-2017 in Hong Kong, China

A new recombinant norovirus, GII.P16-GII.2, emerged in the winter of 2016-2017. Here, we report the complete genome of this strain (Hu/GII/HK/2016/GII.P16-GII.2/CUHK-NS-1082), which was collected from a patient hospitalized with gastroenteritis in September 2016 in Hong Kong, China, and sequenced using next-generation sequencing. This genome had a 95.2% nucleotide identity to the closest sequence in GenBank.

Genotype analysis of noroviruses associated with gastroenteritis outbreaks in childcare centres, Victoria, Australia, 2012-2015

The characteristics of norovirus outbreaks in children (0-5 years) in childcare centres in Victoria, Australia (2012-2015) were examined. The three most common open reading frame (ORF) 2 genotypes in childcare centre outbreaks were GII.4 (42%), GII.6 (21%) and GII.3 (14%); the remaining genotypes (GI.2, GI.3, GI.4, GI.8, GI.13, GII.1, GII.2, GII.7 and GII.13) each made up <10%. The GII.4 genotype was the only norovirus genotype seen in all 4 years of the study and was the most common genotype in 2012-2014 but in 2015 the most common genotype was GII.2. The GII.4 genotype was more common in children 0-2 years, whereas GII.2 and GII.7 were more common in children 4-5 years. ORF 1/ORF 2 recombinant forms identified were GII.P4_NewOrleans_2009/GII.4_Sydney_2012, GII.P12/GII.3, GII.Pb (GII.21)/GII.3, GII.Pe/GII.2, GII.Pe/GII.4_Sydney_2012 and GII.Pg/GII.1. The findings indicate that norovirus genotype prevalence patterns in children were influenced by the age of the children and the year in which the analysis was carried out. The majority of norovirus infections (84%) occurred after the first year of life so that vaccination before the age of one would appear to be the most efficacious.

Norovirus genotype distribution in outbreaks of acute gastroenteritis among children and older people: an 8-year study

Background

Noroviruses (NoVs) are the most frequent cause of acute gastroenteritis worldwide among people of all ages and the leading cause of gastrointestinal disease outbreaks in various settings. To clarify the differences in epidemic situations among different settings, we investigated epidemiological trends and the distribution of NoV genotypes in Yokohama, Japan.

Methods

Between September 2007 and August 2015, 746 outbreaks of NoV gastroenteritis were reported in kindergarten/nursery schools (K/Ns), primary schools (PSs), and nursing homes for the aged (NHs). Stool samples were collected for NoV testing, and the NoV gene was amplified and sequenced to determine the genotype.

Results

During the eight seasons, 248 NoV outbreaks occurred in K/Ns, 274 outbreaks in PSs, and 224 outbreaks in NHs. These outbreaks occurred throughout the year, except in August, and the number increased in November and peaked in December. The number of outbreaks that occurred from November to February comprised 76.8 % of all outbreaks. The outbreaks originated in K/Ns or PSs in every season, except for one season. Five genogroup (G)I and nine GII genotypes in K/Ns, six GI and 10 GII genotypes in PSs, and three GI and six GII genotypes in NHs were detected during the eight seasons. GII.4 was the most prevalent genotype in K/Ns and NHs. However, GII.6 was the most prevalent genotype in PSs. The epidemic genotypes in K/Ns and PSs changed by NoV season, although GII.4 was always predominant in NHs. Moreover, the distribution of genotypes was significantly different between epidemic and non-epidemic periods in each facility (p < 0.01 for all).

Conclusions

The epidemic situation of NoV outbreaks differs by facility, NoV season, and month. The genotype distribution is likely dependent on the facility and is significantly different between epidemic and non-epidemic periods.

Prevalence and molecular characterization of human noroviruses and sapoviruses in Ethiopia

Viral gastroenteritis is a major public health problem worldwide. In Ethiopia, very limited studies have been done on the epidemiology of enteropathogenic viruses. The aim of this study was to detect and characterize noroviruses (NoVs) and sapoviruses (SaVs) from acute gastroenteritis patients of all ages. Fecal samples were collected from diarrheic patients (n = 213) in five different health centers in Addis Ababa during June-September 2013. The samples were screened for caliciviruses by reverse transcription polymerase chain reaction (RT-PCR) using universal and genogroup-specific primer pairs. Phylogenetic analyses were conducted using the sequences of the PCR products. Of the clinical samples, 25.3 % and 4.2 % were positive for NoV and SaV RNA, respectively. Among the norovirus positives, 22 were sequenced further, and diverse norovirus strains were identified: GI (n = 4), GII (n = 17) and GIV (n = 1). Most strains were GII (n = 17/22: 77.2 %), which were further divided into three different genotypes (GII.4, GII.12/GII.g recombinant-like and GII.17), with GII.17 being the dominant (7/17) strain detected. GI noroviruses, in particular GI.4 (n = 1), GI.5 (n = 2) and GI.8 (n = 1), were also detected and characterized. The GIV strain detected is the first from East Africa. The sapoviruses sequenced were also the first reported from Ethiopia. Collectively, this study showed the high burden and diversity of noroviruses and circulation of sapoviruses in diarrheic patients in Ethiopia. Continued surveillance to assess their association with diarrhea is needed to define their epidemiology, disease burden, and impact on public health.

Temporal dynamics of norovirus determined through monitoring of municipal wastewater by pyrosequencing and virological surveillance of gastroenteritis cases

Norovirus is a leading etiological agent of viral gastroenteritis. Because of relatively mild disease symptoms and frequent asymptomatic infections, information on the ecology of this virus is limited. Our objective was to examine the genetic diversity of norovirus circulating in the human population by means of genotyping the virus in municipal wastewater. We investigated norovirus genogroups I and II (GI and GII) in municipal wastewater in Japan by pyrosequencing and quantitative PCR (qPCR) from November 2012 to March 2013. Virological surveillance for gastroenteritis cases was concurrently conducted in the same area. A total of fourteen distinct genotypes in total (GI.1, 3, 4, 6, 7, GII.2, 4, 5, 6, 7, 12, 13, 14, and 17), with up to eight genotypes detected per sample, were observed in wastewater using pyrosequencing; only four genotypes (GI.6, GII.4, 5, and 14) were obtained from clinical samples. Seventy-eight percent of norovirus-positive stool samples contained GII.4, but this genotype was not dominant in wastewater. The norovirus GII.4 Sydney 2012 variant, which appeared and spread during our study period, was detected in both the wastewater and clinical samples. These results suggest that an environmental approach using pyrosequencing yields a more detailed distribution of norovirus genotypes/variants. Thus, wastewater monitoring by pyrosequencing is expected to provide an effective analysis of the distribution of norovirus genotypes causing symptomatic and asymptomatic infections in human populations.

Norovirus diarrhea in Bangladesh, 2010-2014: prevalence, clinical features, and genotypes

Norovirus infections in diarrhea patients attending an urban and a rural hospital in Bangladesh were investigated. A total of 953 fecal specimens from both children and adults collected during 2010-2014 were tested for the presence of norovirus using real time PCR. One fourth (25%) of the specimens were positive for norovirus RNA which was identified both in children and adults. Norovirus was associated with short duration of diarrhea, high abdominal pain, and more moderate to severe dehydration when compared with rotavirus infections. Norovirus GII (69%) was the most prevalent genogroup followed by GI (18%), mixed GI/GII/GIV (11%), and GIV (2%). Among GII genogroup, GII.4 (42%) was the most prevalent genotype followed by GII.3 (21%), GII.6 (7%), GII.7 (6%), and GII.21 (6%). GII.4 and GII.3 strains were frequently identified (82% and 75%, respectively) in children <2 years of age and less commonly (16% and 15%) in adults more than 18 years of age. The present study reinforces the importance of norovirus-associated hospitalizations both in children and adults. The dynamic molecular epidemiology of norovirus requires routine strain surveillance to identify changes in prevailing strains. J. Med. Virol. 88:1742-1750, 2016. © 2016 Wiley Periodicals, Inc.

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.

Rapid emergence and predominance of a broadly recognizing and fast-evolving norovirus GII.17 variant in late 2014

Norovirus genogroup II genotype 4 (GII.4) has been the predominant cause of viral gastroenteritis since 1996. Here we show that during the winter of 2014-2015, an emergent variant of a previously rare norovirus GII.17 genotype, Kawasaki 2014, predominated in Hong Kong and outcompeted contemporary GII.4 Sydney 2012 in hospitalized cases. GII.17 cases were significantly older than GII.4 cases. Root-to-tip and Bayesian BEAST analyses estimate GII.17 viral protein 1 (VP1) evolves one order of magnitude faster than GII.4 VP1. Residue substitutions and insertion occur in four of five inferred antigenic epitopes, suggesting immune evasion. Sequential GII.4-GII.17 infections are noted, implicating a lack of cross-protection. Virus bound to saliva of secretor histo-blood groups A, B and O, indicating broad susceptibility. This fast-evolving, broadly recognizing and probably immune-escaped emergent GII.17 variant causes severe gastroenteritis and hospitalization across all age groups, including populations who were previously less vulnerable to GII.4 variants; therefore, the global spread of GII.17 Kawasaki 2014 needs to be monitored.

Complete Genome Sequence of a Novel Recombinant GII.Pe_GII.17 Norovirus Strain from Hong Kong in 2015

The complete genome sequence of a novel recombinant GII.Pe_GII.17 norovirus strain, tentatively named GII.17 Hong Kong 2015, was determined. RNA-dependent RNA polymerase has 95.6% and 98.4% and viral protein 1 has 90.6% and 95.9% identity at the nucleotide and amino acid levels, respectively, to the closest sequences in GenBank.