Genotypic and epidemiologic trends of norovirus outbreaks in the United States, 2009 to 2013. J Clin Microbiol. 2014;52:147-155. [PMID: 24172151 DOI: 10.1128/jcm.02680-13]

Monomeric catechin and dimeric procyanidin B2 against human norovirus surrogates and their physicochemical interactions

Plant polyphenols have shown antiviral activity against several human pathogens, but their physicochemical interactions are not well-understood. The objectives of this study were to compare the antiviral activity between monomeric catechin and dimeric procyanidin B2 (PB2) using cultivable human norovirus surrogates (feline calicivirus (FCV-F9) and murine norovirus (MNV-1)) and to understand their potential antiviral mechanism using virus-like particles (VLPs) and the P domain of human norovirus GII (HNoV GII.4). Surrogate viruses at 5 log PFU/mL were treated with 0.5–5 mg/mL monomeric catechin monohydrate, PB2 or phosphate buffered saline (PBS, pH 7.2; control) at 37 °C over 24 h. Infectivity was determined using plaque assays and data from triplicate experiments were statistically analyzed. PB2 at 0.5 mg/mL and 1 mg/mL reduced FCV-F9 to undetectable levels after 3 h and MNV-1 by 0.21 and 1.23 log PFU after 24 h, respectively. Monomeric catechins at 1 mg/mL reduced FCV-F9 to undetectable levels after 6 h and MNV-1 titers to undetectable levels after 24 h. In addition, PB2 was shown to directly bind the P domain, the main capsid structure of HNoVs in the ratio of 1:1 through spontaneous interactions. Electrostatic interactions played a dominant role between PB2 and the P domain. PB2 significantly altered tertiary but not secondary structures of VLPs. Transmission electron microscopy demonstrated that PB2 aggregated VLPs, further indicating interactions between them. These findings indicate that PB2 causes structural changes of the P domain of VLPs, mainly through direct interaction leading to HNoV inactivation.

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Polymeric procyanidins cause higher reduction of human norovirus surrogate titers than monomers.

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Binding of procyanidin to human norovirus-like particles alters capsid structure.

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Procyanidin binding to viral capsid results in decreased infectivity.

Genetic Diversity Among Genogroup II Noroviruses and Progressive Emergence of GII.17 in Wastewaters in Italy (2011-2016) Revealed by Next-Generation and Sanger Sequencing

Noroviruses (NoV) are a major cause of gastroenteritis worldwide. Recently, a novel variant of NoV GII.17 (GII.P17_GII.17 NoV), termed Kawasaki 2014, has been increasingly reported in NoV outbreaks in Asia, and has also been described in Europe and North America. In this study, sewage samples were investigated to study the occurrence and genetic diversity of NoV genogroup II (GII) along a 6-year period. Moreover, the spread of GII.17 strains (first appearance and occurrence along time) was specifically assessed. A total of 122 sewage samples collected from 2011 to 2016 from four wastewater treatment plants in Rome (Italy) were initially tested using real-time RT-(q)PCR for GII NoV. Positive samples were subsequently subjected to genotypic characterization by RT-nested PCRs using broad-range primes targeting the region C of the capsid gene of GII NoV, and specific primers targeting the same region of GII.17 NoV. In total, eight different genotypes were detected with the broad-range assay: GII.1 (n = 6), GII.2 (n = 8), GII.3 (n = 3), GII.4 (n = 13), GII.6 (n = 3), GII.7 (n = 2), GII.13 (n = 2), and GII.17 (n = 3), with the latter two genotypes detected only in 2016. Specific amplification of GII.17 NoV was successful in 14 out of 110 positive samples, spanned over the years 2013-2016. The amplicons of the broad-range PCR, pooled per year, were further analyzed by next-generation sequencing (NGS) for a deeper analysis of the genotypes circulating in the study period. NGS confirmed the circulation of GII.17 NoV since 2013 and detected, beyond the eight genotypes identified by Sanger sequencing, three additional genotypes regarded as globally uncommon: GII.5, GII.16, and GII.21. This study provides evidence that GII.17 NoV Kawasaki has been circulating in the Italian population before its appearance and identification in clinical cases, and has become a major genotype in 2016. Our results confirm the usefulness of wastewater surveillance coupled with NGS to study the molecular epidemiology of NoV and to monitor the emergence of NoV strains.

Complete Genome Sequence of a Human Norovirus Strain from the United States Classified as Genotype GII.P6_GII.6

We report here the complete genome sequence of a GII.6 norovirus strain detected in a clinical fecal specimen from the United States. The virus genome has a length of 7,547 bp and a GC content of 50.1%. Complete norovirus genotyping of the full-genome sequence identified the virus genotype as GII.P6_GII.6.

Epidemiology of Foodborne Norovirus Outbreaks - United States, 2009-2015

Noroviruses are the leading cause of acute gastroenteritis and foodborne disease in the United States (U.S.). About 1 in 5 reported norovirus outbreaks are spread through foodborne transmission, presenting opportunities for prevention. We describe the epidemiology of U.S. foodborne norovirus outbreaks reported to national surveillance systems, including differences between genotypes. Foodborne outbreaks that occurred during August 2009-July 2015 with norovirus reported as a single confirmed etiology to the National Outbreak Reporting System (NORS) were matched with outbreaks reported to CaliciNet, a U.S. laboratory norovirus outbreak surveillance network. We analyzed these matched outbreaks stratified by genotype for epidemiologic characteristics, including setting, size and duration, health outcomes of case-patients, implicated food, and outbreak contributing factors. Four hundred ninety-three confirmed foodborne norovirus outbreaks were reported in both NORS and CaliciNet. The most common norovirus genotypes reported were GII.4 (52%), GII.6 (9%), and GI.3 (8%). Compared to non-GII.4 outbreaks, GII.4 outbreaks had higher hospitalization rates (12.8 vs. 4.8 per 1,000 cases, P < 0.01). While contaminated foods were identified and reported in only 35% of outbreaks, molluscan shellfish (4% overall) were more often implicated in non-GII.4 outbreaks than in GII.4 outbreaks (7% vs. 1%, P = 0.04). Of the 240 outbreaks reporting at least one contributing factor, food workers were implicated as the source of contamination in 182 (76%), with no difference between GII.4 and non-GII.4 (73% vs 79%, P = 0.3). Foodborne norovirus outbreaks are frequently reported in the U.S., most of which are caused by GII.4 noroviruses. Viruses of this genotype are associated with higher rates of hospitalization; non-GII.4 noroviruses are more frequently associated with contaminated molluscan shellfish. These surveillance data highlight the diversity of noroviruses causing foodborne disease and can help guide appropriate food safety interventions, including worker hygiene, improved food handling and preparation, and further development of norovirus vaccines.

Prevalence of Human Noroviruses in Commercial Food Establishment Bathrooms

Although transmission of human norovirus in food establishments is commonly attributed to consumption of contaminated food, transmission via contaminated environmental surfaces, such as those in bathrooms, may also play a role. Our aim was to determine the prevalence of human norovirus on bathroom surfaces in commercial food establishments in New Jersey, Ohio, and South Carolina under nonoutbreak conditions and to determine characteristics associated with the presence of human norovirus. Food establishments (751) were randomly selected from nine counties in each state. Four surfaces (underside of toilet seat, flush handle of toilet, inner door handle of stall or outer door, and sink faucet handle) were swabbed in male and female bathrooms using premoistened macrofoam swabs. A checklist was used to collect information about the characteristics, materials, and mechanisms of objects in bathrooms. In total, 61 (1.5%) of 4,163 swabs tested were presumptively positive for human norovirus, 9 of which were confirmed by sequencing. Some factors associated with the presence of human norovirus included being from South Carolina (odd ratio [OR], 2.4; 95% confidence interval [CI], 1.2 to 4.9; P < 0.05) or New Jersey (OR, 1.7; 95% CI, 0.9 to 3.3; 0.05 < P < 0.10), being a chain establishment (OR, 1.9; 95% CI, 1.1 to 3.3; P < 0.05), being a unisex bathroom (versus male: OR, 2.0; 95% CI, 0.9 to 4.1; 0.05 < P < 0.10; versus female: OR, 2.6; 95% CI, 1.2 to 5.7; P < 0.05), having a touchless outer door handle (OR, 3.3; 95% CI, 0.79 to 13.63; 0.05 < P < 0.10), and having an automatic flush toilet (OR, 2.5, 95% CI, 1.1 to 5.3; 0.05 < P < 0.10). Our findings confirm that the presence of human norovirus on bathroom surfaces in commercial food establishments under nonoutbreak conditions is a rare event. Therefore, routine environmental monitoring for human norovirus contamination during nonoutbreak periods is not an efficient method of monitoring norovirus infection risk.

Waterborne Norovirus outbreak at a seaside resort likely originating from municipal water distribution system failure

In May 2016 a Norovirus (NoV) gastroenteritis outbreak involved a high school class visiting a seaside resort near Taormina (Mascali, Sicily). Twenty-four students and a teacher were affected and 17 of them showed symptoms on the second day of the journey, while the others got ill within the following 2 days. Symptoms included vomiting, diarrhoea and fever, and 12 students required hospitalisation. Stool samples tested positive for NoV genome by Real-Time polymerase chain reaction assay in all 25 symptomatic subjects. The GII.P2/GII.2 NoV genotype was linked to the outbreak by ORF1/ORF2 sequence analysis. The epidemiological features of the outbreak were consistent with food/waterborne followed by person-to-person and/or vomit transmission. Food consumed at a shared lunch on the first day of the trip was associated to illness and drinking un-bottled tap water was also considered as a risk factor. The analysis of water samples revealed the presence of bacterial indicators of faecal contamination in the water used in the resort as well as in other areas of the municipal water network, linking the NoV gastroenteritis outbreak to tap water pollution from sewage leakage. From a single water sample, an amplicon whose sequence corresponded to the capsid genotype recovered from patients could be obtained.

Evaluation of RIDA®GENE norovirus GI/GII real time RT-PCR using stool specimens collected from children and adults with acute gastroenteritis

BACKGROUND

Norovirus is the leading cause of epidemic and sporadic acute gastroenteritis (AGE) in the United States. Widespread prevalence necessitates implementation of accurate norovirus detection assays in clinical diagnostic laboratories.

OBJECTIVE

To evaluate RIDA^®GENE norovirus GI/GII real-time RT-PCR assay (RGN RT-PCR) using stool samples from patients with sporadic AGE.

STUDY DESIGN

Patients between 14 days to 101 years of age with symptoms of AGE were enrolled prospectively at four sites across the United States during 2014-2015. Stool specimens were screened for the presence of norovirus RNA by the RGN RT-PCR assay. Results were compared with a reference method that included conventional RT-PCR and sequencing of a partial region of the 5'end of the norovirus ORF2 gene.

RESULTS

A total of 259 (36.0%) of 719 specimens tested positive for norovirus by the reference method. The RGN RT-PCR assay detected norovirus in 244 (94%) of these 259 norovirus positive specimens. The sensitivity and specificity (95% confidence interval) of the RGN RT-PCR assay for detecting norovirus genogroup (G) I was 82.8% (63.5-93.5) and 99.1% (98.0-99.6) and for GII was 94.8% (90.8-97.2) and 98.6% (96.9-99.4), respectively. Seven specimens tested positive by the RGN-RT PCR that were negative by the reference method. The fifteen false negative samples were typed as GII.4 Sydney, GII.13, GI.3, GI.5, GI.2, GII.1, and GII.3 in the reference method.

CONCLUSIONS

The RGN RT-PCR assay had a high sensitivity and specificity for the detection of norovirus in stool specimens from patients with sporadic AGE.

Prevalence and genetic diversity of norovirus genogroup II in children less than 5 years of age with acute gastroenteritis in Tehran, Iran

Viral gastroenteritis is a major public health problem worldwide. In Iran, very limited studies have been performed with regard to the epidemiology of noroviruses. This study aimed to evaluate the prevalence and molecular epidemiology of GII noroviruses in hospitalized children less than 5 years of age with acute gastroenteritis (AGE). A total of 210 stool specimens were collected from Ali Asghar Children's Hospital and Bahrami Children's Hospital in Tehran, from June 2015 to June 2016. The samples were screened by real-time RT-PCR for genogroup II (GII). Positive samples were genotyped by semi-nested PCR followed by Sanger sequencing and phylogenetic analysis. Norovirus was identified in 36 (17.1%) of 210 specimens. Based on genetic analysis of RdRp and capsid sequences, the strains were clustered into eight RdRp-capsid genotypes: GII.P4-GII.4 Sydney_2012 (41.7%), GII.Pe-GII.4 Sydney_2012 (30.6%), GII.P21-GII.3 (13.9%), GII.P16-GII.4 Sydney_2012 (2.8%), GII.P16-GII.12 (2.8%), GII.P2-GII.4 Sydney_2012 (2.8%), GII.P7-GII.7 (2.8%) and GII.P2-GII.2 (2.8%). We determined several different co-circulating norovirus genotypes in children < 5 years of age with AGE in our hospital in Tehran, Iran. Continued molecular surveillance of noroviruses, including typing of both RdRp and capsid genes, is important for monitoring emerging strains in our continued efforts to reduce the overall burden of norovirus disease.

Molecular epidemiology and temporal evolution of norovirus associated with acute gastroenteritis in Amazonas state, Brazil

BACKGROUND

Globally, Norovirus (NoV) is considered the most common cause of diarrheal episodes across all age groups. Despite its wide genetic diversity, the GII.4 strain is the most predominant and has been associated with epidemics worldwide. In this study, we characterized sporadic cases of diarrhea from NoV-positive children, during a five-year period (2010-2014).

METHODS

A total of 250 NoV-positive samples identified by an enzyme immunoassay (EIA) were subjected to RT-PCR and partial nucleotide sequencing for polymerase and capsid genes. Phylogenetic analysis was performed to identify NoV genotypes using the binary classification. In addition, sequences from the P2 subdomain (capsid) gene of GII-4 variants were characterized by evolutionary analyses, using the MCMC method implemented in the BEAST package. A 3D structure was built using protein modeling.

RESULTS

Phylogenetic analysis demonstrated a predominance of genotype GII.4 (52.4% - 99/189), variants New Orleans_2009 and Sydney_2012 followed by GII.P7/GII.6 with 6.3% (12/189). Amino acid analyses of the GII.4 strains showed several important amino acid changes. A higher evolutionary rate was found, 7.7 × 10^- 3 in the Sydney variant and 6.3 × 10^- 3 in the New Orleans. Based in evolutionary analysis the time to the most recent common ancestor (TMRCA) has been calculated as estimates of the population divergence time. Thus, TMRCA for New Orleans and Sydney variant were 2008.7 and 2010.7, respectively. Also, we observed a lineage of transition between New Orleans and Sydney.

CONCLUSION

This study describes the different strains of norovirus isolated from Amazonas state in Brazil during a five-year period. Considering that NoV are capable of changing their antigenic epitopes rapidly, a continuous surveillance is important to monitor the occurrence and changes of the NoV in the community through epidemiological studies. These results contribute to the understanding of NoV molecular epidemiology and its evolutionary dynamics in Amazonas state, Brazil.

Temporal evolutionary analysis of re-emerging recombinant GII.P16_GII.2 norovirus with acute gastroenteritis in patients from Hubei Province of China, 2017

Norovirus (NoV) is a major pathogenic agent of human acute viral gastroenteritis that occurs worldwide. In March 2017, a series of acute NoV-associated gastroenteritis outbreaks occurred in Hubei Province in central China. Here, we sought to better understand the main genotypes and potential evolutionary advantages of circulating NoV strains underlying these outbreaks. During the outbreak, 111 fecal swabs and stool samples were collected from outpatients with acute NoV-associated gastroenteritis in Hubei Province. RNA was extracted from the samples and used as a template for real-time RT-PCR. Sequencing of a portion of the capsid gene and the ORF1/ORF2 overlap was used to assess DNA sequence homology, phylogeny, and recombination using pairwise alignments, MEGA, and Simplot, respectively. Bayesian evolutionary inference analysis was performed using the BEAST software platform to assess the genetic relationships, evolution rate, and evolutionary history of norovirus. GII NoV was determined to be the major pathogen of the acute gastroenteritis outbreaks in Hubei Province, with a 57.7% positive rate. Homology and phylogenic analysis of a portion of the capsid region for GII NoV isolates collected during outbreaks in Hubei showed that the isolates had a very high sequence identity and belonged to GII.2 genotype. Phylogenetic analysis of recombination using the ORF1/ORF2 overlap region revealed a recombinant strain, GII.P16_GII.2, in samples isolated from Hubei Province. The partial polymerase region and capsid gene of the recombinant strain had very high identity (98.7-98.8%) with the NoV strains isolated in Germany in 2016. The evolutionary rate of VP1 gene of GII.2 was distinctly higher than that of the partial polymerase region of GII.16. A phylogenetic tree generated using MCMC showed that the recombinant NoV GII.16_GII.2 was significantly divergent from other GII.16_GII.2 strains observed in China and Japan. Continued circulation of this GII.16_GII.2 recombinant could overtake the predominant GII.4 NoV strain with geographic expansion. Further analysis of the evolutionary dynamics of norovirus is necessary to develop more effective prevention and control strategies.

The influence of food matrices on aptamer selection by SELEX (systematic evolution of ligands by exponential enrichment) targeting the norovirus P-Domain

This study investigates the enrichment of aptamers targeting the norovirus protruding domain in the presence of foods often associated with norovirus outbreaks. The goal is to explore if and how the presence of food alters in vitro selection of aptamers and target binding of the enriched oligonucleotides. Our study demonstrates that the introduction of food to SELEX (systematic evolution of ligands by exponential enrichment) is either detrimental to enrichment of oligonucleotides with target-specific binding, or facilitates enrichment of non-target-specific oligonucleotides. Moreover, a relationship between target binding of enriched oligonucleotides in presence of food and their selection condition was not observed. Our findings also suggest that a pathogen specific aptamer with application in food does not need to be selected in presence of the particular food, but may require properties beyond high affinity and selectivity to be applied for pathogen extraction and detection in undiluted food matrices.

Norovirus Illnesses in Children and Adolescents

Norovirus is a leading cause of childhood vomiting and diarrhea in the United States and globally. Although most illnesses caused by norovirus are self-resolving, severe outcomes may occur from dehydration, including hospitalization and death. A vast majority of deaths from norovirus occur in developing countries. Immunocompromised children are at risk for more severe outcomes. Treatment of norovirus illness is focused on early correction of dehydration and maintenance of fluid status and nutrition. Hand hygiene, exclusion of ill individuals, and environmental cleaning are important for norovirus outbreak prevention and control, and vaccines to prevent norovirus illness are currently under development.

Non-stop aptasensor capable of rapidly monitoring norovirus in a sample

A cost-effective and simple biosensor was developed for the accurate and rapid monitoring of norovirus GII in a sample. The modified DNA aptamer, 5 guanines linked to conventional DNA aptamer, designed for the research, was able to rapidly capture norovirus GII in tap water as well artificial urine. In addition, the extra guanines of the modified DNA aptamer enhanced the sensitivity of biosensor with guanine chemiluminescence detection based on the principle of intra chemiluminescent resonance transfer (Intra-CRET). This is because additional high-energy intermediates formed from the reaction of extra guanines and 3, 4, 5-trimethoxylphenylglyoxal (TMPG) were able to directly transfer energy to 6-carboxylfluorescein (6-FAM) to emit bright chemiluminescence. The biosensor operated without time-consuming and tedious procedures (e.g., sample pretreatment, long and multiple incubations, washings) was able to accurately quantify trace levels of norovirus GII capsid with excellent specificity and reproducibility. The limit of detection (LOD = 3σ) of the biosensor for norovirus GII capsids in tap water was as low as 80 ng/ml. It is expected that the new technology confirmed while developing the biosensor can be applied to devise alternative biosensors capable of rapidly quantifying various food-borne pathogens in a sample.

Significance of continuous rotavirus and norovirus surveillance in Indonesia

BACKGROUND

Diarrhea significantly contributes to the global burden of diseases, particularly in developing countries. Rotavirus and norovirus are the most dominant viral agents responsible for diarrheal disease globally. The aim of this review was to conduct a comprehensive assessment of rotavirus and norovirus study in Indonesia.

DATA SOURCES

Articles about rotavirus and norovirus surveillance in Indonesia were collected from databases, including PubMed and Google Scholar. Manual searching was performed to identify additional studies. Furthermore, relevant articles about norovirus diseases were included.

RESULTS

A national surveillance of rotavirus-associated gastroenteritis has been conducted for years, resulting in substantial evidence about the high burden of the diseases in Indonesia. In contrast, norovirus infection received relatively lower attention and very limited data are available about the incidence and circulating genotypes. Norovirus causes sporadic and epidemic gastroenteritis globally. It is also emerging as a health problem in immunocompromised individuals. During post-rotavirus vaccination era, norovirus potentially emerges as the most frequent cause of diarrheal diseases.

CONCLUSIONS

Our review identifies knowledge gaps in Indonesia about the burden of norovirus diseases and the circulating genotypes. Therefore, there is a pressing need to conduct national surveillance to raise awareness of the community and national health authority about the actual burden of norovirus disease in Indonesia. Continuing rotavirus surveillance is also important to assess vaccine effectiveness and to continue tracking any substantial changes of circulating rotavirus genotypes.

Molecular surveillance of norovirus, 2005-16: an epidemiological analysis of data collected from the NoroNet network

BACKGROUND

The development of a vaccine for norovirus requires a detailed understanding of global genetic diversity of noroviruses. We analysed their epidemiology and diversity using surveillance data from the NoroNet network.

METHODS

We included genetic sequences of norovirus specimens obtained from outbreak investigations and sporadic gastroenteritis cases between 2005 and 2016 in Europe, Asia, Oceania, and Africa. We genotyped norovirus sequences and analysed sequences that overlapped at open reading frame (ORF) 1 and ORF2. Additionally, we assessed the sampling date and country of origin of the first reported sequence to assess when and where novel drift variants originated.

FINDINGS

We analysed 16 635 norovirus sequences submitted between Jan 1, 2005, to Nov 17, 2016, of which 1372 (8·2%) sequences belonged to genotype GI, 15 256 (91·7%) to GII, and seven (<0·1%) to GIV.1. During this period, 26 different norovirus capsid genotypes circulated and 22 different recombinant genomes were found. GII.4 drift variants emerged with 2-3-year periodicity up to 2012, but not afterwards. Instead, the GII.4 Sydney capsid seems to persist through recombination, with a novel recombinant of GII.P16-GII.4 Sydney 2012 variant detected in 2014 in Germany (n=1) and the Netherlands (n=1), and again in 2016 in Japan (n=2), China (n=8), and the Netherlands (n=3). The novel GII.P17-GII.17, first reported in Asia in 2014, has circulated widely in Europe in 2015-16 (GII.P17 made up a highly variable proportion of all sequences in each country [median 11·3%, range 4·2-53·9], as did GII.17 [median 6·3%, range 0-44·5]). GII.4 viruses were more common in outbreaks in health-care settings (2239 [37·2%] of 6022 entries) compared with other genotypes (101 [12·5%] of 809 entries for GI and 263 [13·5%] of 1941 entries for GII non-GII.Pe-GII.4 or GII.P4-GII.4).

INTERPRETATION

Continuous changes in the global norovirus genetic diversity highlight the need for sustained global norovirus surveillance, including assessment of possible immune escape and evolution by recombination, to provide a full overview of norovirus epidemiology for future vaccine policy decisions.

FUNDING

European Union's Horizon 2020 grant COMPARE, ZonMw TOP grant, the Virgo Consortium funded by the Dutch Government, and the Hungarian Scientific Research Fund.

High Hand Contamination Rates During Norovirus Outbreaks in Long-Term Care Facilities

We examined norovirus contamination on hands of ill patients during 12 norovirus outbreaks in 12 long-term care facilities (LTCFs). The higher frequency and norovirus titers on hands of residents compared to hands of heathcare workers highlights the importance of adhering to appropriate hand hygiene practices during norovirus outbreaks in LTCFs. Infect Control Hosp Epidemiol 2018;39:219-221.

Development of a Surrogate Neutralization Assay for Norovirus Vaccine Evaluation at the Cellular Level

Noroviruses (NoVs) are the main pathogens responsible for sporadic and epidemic nonbacterial gastroenteritis, causing an estimated 219,000 deaths annually worldwide. There is no commercially available vaccine for NoVs, due partly to the difficulty in establishing NoV cell culture models. The histo-blood group antigen (HBGA) blocking assay is used extensively to assess the protective potential of candidate vaccine-elicited antibodies, but there is still no widely used cellular evaluation model. In this study, we have established a cell line-based NoV vaccine evaluation model through the construction of human α1,2-fucosyltransferase 2-overexpressing 293T (293T-FUT2) cell lines. The 293T-FUT2 cells stably expressed H type 2 and Lewis y antigens. Virus-like particles (VLPs) of the NoV prototype strain genogroup I.1 (GI.1) and the predominant strains GII.4 and GII.17 could attach to the cell line efficiently in a dose-dependent manner. Importantly, antisera against these NoV VLPs could inhibit the attachment of the VLPs, where the inhibitory effects measured by the attachment inhibition assay correlated significantly with the antibody levels determined by the HBGA blocking assay. Collectively, our attachment inhibition assay could serve as a surrogate neutralization assay for the evaluation of NoV vaccines at the cellular level.

The unwelcome houseguest: secondary household transmission of norovirus

Norovirus is the leading cause of acute gastroenteritis in the USA. Although secondary household transmission of norovirus is frequently reported in outbreaks, little is known about specific risk factors for susceptibility and infectiousness in the household. Three norovirus outbreaks were investigated and data were collected on individuals exposed in the primary outbreak setting and their household members. Potential individual- and household-level risk factors for susceptibility and infectiousness were assessed using univariate and multivariate generalised linear mixed models. In the univariate models, the secondary attack rate (SAR) was significantly higher when living in a household with two or more primary cases (incidence rate ratio (IRR) = 2·1; 95% confidence interval (CI) 1·37-3·29), more than one primary case with vomiting (IRR = 1·9; CI 1·11-3·37), and at least one primary case with diarrhoea (IRR = 3·0; CI 1·46-6·01). After controlling for other risk factors in the multivariate models, the SAR was significantly higher among those living in a household with two or more primary cases (adjusted IRR = 2·0; CI 1·17-3·47) and at least one primary case with diarrhoea (adjusted IRR = 2·8; CI 1·35-5·93). These findings underscore the importance of maintaining proper hygiene and isolating ill household members to prevent norovirus transmission in the household.

Molecular Evolution of the VP1 Gene in Human Norovirus GII.4 Variants in 1974-2015

Human norovirus (HuNoV) is a leading cause of viral gastroenteritis worldwide, of which GII.4 is the most predominant genotype. Unlike other genotypes, GII.4 has created various variants that escaped from previously acquired immunity of the host and caused repeated epidemics. However, the molecular evolutionary differences among all GII.4 variants, including recently discovered strains, have not been elucidated. Thus, we conducted a series of bioinformatic analyses using numerous, globally collected, full-length GII.4 major capsid (VP1) gene sequences (466 strains) to compare the evolutionary patterns among GII.4 variants. The time-scaled phylogenetic tree constructed using the Bayesian Markov chain Monte Carlo (MCMC) method showed that the common ancestor of the GII.4 VP1 gene diverged from GII.20 in 1840. The GII.4 genotype emerged in 1932, and then formed seven clusters including 14 known variants after 1980. The evolutionary rate of GII.4 strains was estimated to be 7.68 × 10⁻³ substitutions/site/year. The evolutionary rates probably differed among variants as well as domains [protruding 1 (P1), shell, and P2 domains]. The Osaka 2007 variant strains probably contained more nucleotide substitutions than any other variant. Few conformational epitopes were located in the shell and P1 domains, although most were contained in the P2 domain, which, as previously established, is associated with attachment to host factors and antigenicity. We found that positive selection sites for the whole GII.4 genotype existed in the shell and P1 domains, while Den Haag 2006b, New Orleans 2009, and Sydney 2012 variants were under positive selection in the P2 domain. Amino acid substitutions overlapped with putative epitopes or were located around the epitopes in the P2 domain. The effective population sizes of the present strains increased stepwise for Den Haag 2006b, New Orleans 2009, and Sydney 2012 variants. These results suggest that HuNoV GII.4 rapidly evolved in a few decades, created various variants, and altered its evolutionary rate and antigenicity.

Variations in status of preparation of personal protective equipment for preventing norovirus gastroenteritis in long-term care facilities for the elderly

RATIONALE, AIM, AND OBJECTIVES

Residents of long-term care facilities are highly susceptible to norovirus gastroenteritis, and each facility is concerned about the need to implement norovirus infection control. Among control measures, personal protective equipment (PPE), such as disposable gloves and masks, plays a major role in reducing infectious spread. However, the preparation status of PPE in facilities before infection outbreaks has not been reported. The aim was to clarify the implementation status of preventive measures for norovirus gastroenteritis and the cost of preparing the necessary PPE in long-term care facilities.

METHOD

A questionnaire survey of facilities affiliated with the Kyoto Prefecture and Osaka Prefecture branches of the Japan Association of Geriatric Health Services Facilities was conducted. The survey items were the characteristics of the facility, whether preventive measures had been implemented for norovirus gastroenteritis from October through the following March in both 2009 and 2010, and the quantities and unit prices of PPE prepared for preventive measures.

RESULTS

Twenty-six (11.2%) of 232 surveyed facilities (as of August 2011) answered the survey. Among them, 24 (92.3%) in 2009 and 25 (96.2%) in 2010 reported having implemented preventive measures for norovirus gastroenteritis, while 21 facilities (80.8%) in 2009 and 22 facilities (84.6%) in 2010 had prepared PPE. The median total cost for preparing the PPE needed for the preventive measures was US $2601 (range US $221-9192) in 2009 and US $3904 (range US $305-6427) in 2010.

CONCLUSION

Although the results need careful interpretation because of the low response rate, most of the surveyed long-term care facilities had implemented preventive measures for norovirus gastroenteritis. However, the cost of preparing the PPE needed for the preventive measures varied among the facilities.

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.

Distribution of Naturally Occurring Norovirus Genogroups I, II, and IV in Oyster Tissues

This study evaluated different tissues of naturally contaminated oysters (Crassostrea belcheri) for the presence of noroviruses. RNA from digestive tissues, gills, and mantle of the oysters was extracted and tested for norovirus genogroup (G) I, GII, and GIV using RT-nested PCR. In spiking experiments with a known norovirus, GII.4, the detection limits were 2.97 × 10² RNA copies/g of digestive tissues, 2.62 × 10² RNA copies/g of gills, and 1.61 × 10³ RNA copies/g of mantle. A total of 85 oyster samples were collected from a fresh market in Bangkok, Thailand. Noroviruses were found in the oyster samples (40/85, 47%): GI (29/85, 34.1%), GII (9/85, 10.5%), mixed GI and GII (1/85, 1.2%), and GIV (1/85, 1.2%). All three genogroups were found in the digestive tissues of oysters. Norovirus GI was present in all three tissues with the highest frequency in the mantle, and was additionally detected in multiple tissues in some oysters. GII was also detected in all three tissues, but was not detected in multiple tissues in the same oyster. For genogroup I, only GI.2 could be identified and it was found in all tissues. For genogroup II, three different genotypes were identified, namely GII.4 which was detected in the gills and the mantle, GII.17 which was detected in the digestive tissues, and GII.21 which was detected in the mantle. GIV.1 was identified in the digestive tissues of one oyster. This is the first report on the presence of human GIV.1 in oyster in Thailand, and the results indicate oyster as a possible vehicle for transmission of all norovirus genogroups in Thailand.

Outbreak of caliciviruses in the Singapore military, 2015

Background

From 31 August to 9 September 2015, a total of 150 military personnel at a military institution in Singapore were infected with acute gastroenteritis (AGE) with an attack rate of approximately 3%. This study aimed to determine the epidemiology of the outbreak, investigate its origins, and discuss measures to prevent future occurrences.

Methods

After the AGE outbreak was declared on 31 August 2015, symptom surveys, hygiene inspections, and the testing of water, food, and stool samples were initiated. We collected 86 stool samples from AGE cases and 58 samples from food-handlers during the course of the outbreak and these stool samples were tested for 8 bacterial pathogens and 2 viral pathogens (i.e., norovirus and sapovirus).

Results

We detected Sapovirus (SaV), group I Norovirus (NoV GI) and group II Norovirus (NoV GII) from the stool samples of AGE cases. Further sequence analyses showed that the AGE outbreak in August was caused mainly by three rarely reported calicivirus novel genotypes: NoV GI.7, NoV GII.17 and SaV GII.3. Control measures implemented focused on the escalation of personal and environmental hygiene, which included the separation of affected and unaffected soldiers, enforcement of rigorous hand-washing and hygiene, raising awareness of food and water safety, and disinfection of communal areas with bleach.

Conclusions

This study identified both NoV and SaV as the causative agents for an AGE outbreak at a Singapore military camp in August 2015. This study is also the first to report SaV as one of the main causative agents, highlighting the importance of caliciviruses as causative agents of AGE outbreaks in the Singapore military. As there are no commercially available vaccines against caliciviruses, strict personal hygiene and proper disinfection of environmental surfaces remain crucial to prevent calicivirus outbreak and transmission.

Performance evaluation of Cepheid Xpert Norovirus kit with a user-modified protocol

The Cepheid Xpert® Norovirus kit automates sample processing, nucleic acid extraction, and real-time reverse transcription polymerase chain reactions (RT-PCRs) to detect norovirus genogroups I (GI) and II (GII). Eighty-five stool samples collected between February 2015 and May 2017 were used to compare the performance of a user-modified Xpert assay against a clinically validated laboratory-developed test (LDT). Of the 85 samples, 54 were previously archived in -80°C freezer. The remaining 31 were fresh samples tested concurrently with the LDT. The results of all samples tested using the Xpert kit and LDT were found to be concordant, including 12 GI- and 42 GII-positive samples, 1 GI and GII coinfection, and 30 negative samples. Comparison of the assays showed perfect concordance with a kappa coefficient score of 1.00 (95%CI from 1.00 to 1.00). Of the 30 negative stool samples tested, three samples were positive for rotavirus detected using an immunochromatographic assay, with no cross-reactivity shown in both LDT and Xpert assays. In-run sample processing control of the Xpert assay for all negative samples tested showed no/minor inhibition. Compared to the LDT, the Xpert assay produced similar or better Ct values for detection. It also showed better mitigation of PCR inhibition in stool sample testing.

Genotypic and Epidemiological Trends of Acute Gastroenteritis Associated with Noroviruses in China from 2006 to 2016

There are periodical norovirus-associated acute gastroenteritis outbreaks around the world. This study aimed to analyze the molecular and epidemiological features of norovirus infections in China during 2006–2016. We extracted epidemiological data from 132 norovirus outbreaks and the norovirus genotyping for 1291 sequences in China over the past ten years. A total of 132 norovirus outbreaks (8133 cases) were reported in China, where the east and south regions were most affected [47.7% (63/132)]. The highest number of outbreaks occurred in 2015. A seasonal pattern has been observed, with a peak from November to the following March. Most of the outbreaks occurred in middle and primary schools, accounting for 28.8% (38/132), and 28.0% (37/132) of outbreaks, respectively. The dominant age group was 10 to 19 years old, responsible for 75.7% (933/1232) of cases. Generally, the dominant genotypes was GII, for 81.9% (1058/1291) of sequences. G II.4 was the predominant genotype in China from 2004 to 2014. However, the GII.17 became more prevalent starting in 2014. Norovirus-associated acute gastroenteritis increased sharply in recent years caused by the emergence of GII.17, but epidemiological features have not changed during 2006–2016. Vigilant surveillance should be strengthened to promptly detect any variation.

Applying Quantitative Molecular Tools for Virus Transport Studies: Opportunities and Challenges

Bacteriophages have been used in soil column studies for the last several decades as surrogates to study the fate and transport behavior of enteric viruses in groundwater. However, recent studies have shown that the transport behavior of bacteriophages and enteric viruses in porous media can be very different. The next generation of virus transport science must therefore provide more data on mobility of enteric viruses and the relationship between transport behaviors of enteric viruses and bacteriophages. To achieve this new paradigm, labor intensity devoted to enteric virus quantification method must be reduced. Recent studies applied quantitative polymerase chain reaction (qPCR) to column filtration experiments to study the transport behavior of human adenovirus (HAdV) in porous media under a variety of conditions. A similar approach can be used to study the transport of other enteric viruses such as norovirus. Analyzing the column samples with both qPCR and culture assays and applying multiplex qPCR to study cotransport behavior of more than one virus will provide information to under-explored areas in virus transport science. Both nucleic acid extraction kits and one-step lysis protocols have been used in these column studies to extract viral nucleic acid for qPCR quantification. The pros and cons of both methods are compared herein and solutions for overcoming problems are suggested. As better understanding of the transport behavior of enteric viruses is clearly needed, we strongly advocate for application of rapid molecular tools in future studies as well as optimization of protocols to overcome their current limitations.

Rotavirus capsid VP6 protein acts as an adjuvant in vivo for norovirus virus-like particles in a combination vaccine

Rotavirus (RV) and norovirus (NoV) are the 2 leading causes of acute viral gastroenteritis worldwide. We have developed a non-live NoV and RV vaccine candidate consisting of NoV virus-like particles (VLPs) and recombinant polymeric RV VP6 protein produced in baculovirus-insect cell expression system. Both components have been shown to induce strong potentially protective immune responses. As VP6 nanotubes are highly immunogenic, we investigated here a possible adjuvant effect of these structures on NoV-specific immune responses in vivo. BALB/c mice were immunized intramuscularly with a suboptimal dose (0.3 μg) of GII.4 or GI.3 VLPs either alone or in a combination with 10 μg dose of VP6 and induction of NoV-specific antibodies in sera of experimental animals were measured. Blocking assay using human saliva or synthetic histo-blood group antigens was employed to test NoV blocking antibodies. Suboptimal doses of the VLPs alone did not induce substantial anti-NoV antibodies. When co-administered with the VP6, considerable titers of not only type-specific but also cross-reactive IgG antibodies against NoV VLP genotypes not included in the vaccine composition were induced. Most importantly, NoV-specific blocking antibodies, a surrogate for neutralizing antibodies, were generated. Our results show that RV VP6 protein has an in vivo adjuvant effect on NoV-specific antibody responses and support the use of VP6 protein as a part of the NoV-RV combination vaccine, especially when addition of external adjuvants is not desirable.

Dissemination of a nonpathogenic viral DNA surrogate marker from high-touch surfaces in rooms of long-term care facility residents

A nonpathogenic DNA marker inoculated onto the television remote controls in rooms of 2 ambulatory long-term care facility (LTCF) residents disseminated to the hands of the LTCF residents, to high-touch surfaces in the room and on the ward, and to shared portable equipment. These findings suggest that contaminated high-touch surfaces in rooms of ambulatory LTCF residents are a potential source for widespread dissemination of pathogens.

Sensitive Genotyping of Foodborne-Associated Human Noroviruses and Hepatitis A Virus Using an Array-Based Platform

Human noroviruses (NoV) are the leading cause of human gastroenteritis in populations of all ages and are linked to most of the foodborne outbreaks worldwide. Hepatitis A virus (HAV) is another important foodborne enteric virus and is considered the most common agent causing acute liver disease worldwide. In the present study, a focused, low-density DNA microarray was developed and validated for the simultaneous identification of foodborne-associated genotypes of NoV and HAV. By employing a novel algorithm, capture probes were designed to target variable genomic regions commonly used for typing these foodborne viruses. Validation results showed that probe signals, specific for the tested NoV or HAV genotypes, were on average 200-times or 38-times higher than those detected for non-targeted genotypes, respectively. To improve the analytical sensitivity of this method, a 12-mer oligonucleotide spacer sequence was added to the capture probes and resulted in a detection threshold of less than 10 cRNA transcripts. These findings have indicated that this array-based typing sensor has the accuracy and sensitivity for identifying NoV and HAV genotypic profiles predominantly linked to food poisoning. The implementation of this typing sensor would thus provide highly relevant and valuable information for use in surveillance and outbreak attribution.

Pathogen-Specific Burden of Outpatient Diarrhea in Infants in Nepal: A Multisite Prospective Case-Control Study

BACKGROUND

Nonsevere diarrheal disease in Nepal represents a large burden of illness. Identification of the specific disease-causing pathogens will help target the appropriate control measures.

METHODS

Infants aged 6 weeks to 12 months were recruited from 5 health facilities in eastern, central, and western Nepal between August 2012 and August 2013. The diarrhea arm included infants with mild or moderate diarrhea treatable in an outpatient setting; the nondiarrhea arm included healthy infants who presented for immunization visits or had a mild nondiarrheal illness. Stool samples were tested for 15 pathogens with a multiplex polymerase chain reaction (PCR) assay and real-time reverse-transcription (RT)-PCR assays for rotavirus and norovirus. Rotavirus- and norovirus-positive specimens were genotyped. We calculated attributable fractions (AFs) to estimate the pathogen-specific burden of diarrhea and adjusted for facility, age, stunting, wasting, and presence of other pathogens.

RESULTS

We tested 307 diarrheal and 358 nondiarrheal specimens. Pathogens were detected more commonly in diarrheal specimens (164 of 307 [53.4%]) than in nondiarrheal specimens (113 of 358 [31.6%]) (P < .001). Rotavirus (AF, 23.9% [95% confidence interval (CI), 14.9%-32.8%]), Salmonella (AF, 12.4% [95% CI, 6.6%-17.8%]), and Campylobacter (AF, 5.6% [95% CI, 1.3%-9.8%]) contributed most to the burden of disease. In these diarrheal specimens, the most common genotypes for rotavirus were G12P[6] (27 of 82 [32.9%]) and G1P[8] (16 of 82 [19.5%]) and for norovirus were GII.4 Sydney (9 of 26 [34.6%]) and GII.7 (5 of 26 [19.2%]).

CONCLUSIONS

The results of this study indicate that the introduction of a rotavirus vaccine in Nepal will likely decrease outpatient diarrheal disease burden in infants younger than 1 year, but interventions to detect and target other pathogens, such as Salmonella and Campylobacter spp, should also be considered.

Comparison of three multiplex gastrointestinal platforms for the detection of gastroenteritis viruses

BACKGROUND

Viruses are major etiological agents of childhood gastroenteritis. In recent years, several molecular platforms for the detection of viral enteric pathogens have become available.

OBJECTIVE/STUDY DESIGN

We evaluated the performance of three multiplex platforms including Biofire's Gastrointestinal Panel (FilmArray), Luminex xTAG^® Gastrointestinal Pathogen Panel (GPP), and the TaqMan Array Card (TAC) for the detection of five gastroenteritis viruses using a coded panel of 300 archived stool samples.

RESULTS

The FilmArray detected a virus in 199 (96.1%) and the TAC in 172 (83.1%) of the 207 samples (187 samples positive for a single virus and 20 samples positive for more than one virus) whereas the GPP detected a virus in 100 (78.7%) of the 127 (97 positive for one virus and three positive for more than one virus) samples. Overall the clinical accuracy was highest for the FilmArray (98%) followed by TAC (97.2%) and GPP (96.9%). The sensitivity of the FilmArray, GPP and TAC platforms was highest for rotavirus (100%, 95.8%, and 89.6%, respectively) and lowest for adenovirus type 40/41 (97.4%, 57.9% and 68.4%). The specificity of the three platforms ranged from 95.6% (rotavirus) to 99.6% (norovirus/sapovirus) for the FilmArray, 99.6% (norovirus) to 100% (rotavirus/adenovirus) for GPP, and 98.9% (astrovirus) to 100% (rotavirus/sapovirus) for TAC.

CONCLUSION

The FilmArray demonstrated the best analytical performance followed by TAC. In recent years, the availability of multi-enteric molecular testing platforms has increased significantly and our data highlight the strengths and weaknesses of these platforms.

Detection of waterborne norovirus genogroup I strains using an improved real time RT-PCR assay

Noroviruses (NoVs) are the major global source of acute gastroenteritis (AGE) outbreaks. To detect NoVs, real-time reverse transcription-quantitative PCR (RT-qPCR) assays have been widely employed since the first decade of the 21^st century. We developed a redesigned probe, JJV1PM, for RT-qPCR assay detection of NoV genogroup (G) I strains. The new RT-qPCR assay using the JJV1PM-probe showed broader strain reactivity for 10 NoV GI genotypes, while the old method, using the JJV1PT-probe assay, detected only 7 NoV GI genotypes in a validation panel using human fecal specimens. The improved RT-qPCR assay was also successfully applied to water samples. The JJV1PM-probe assay identified 7 NoV GI genotypes, whereas the JJV1PT-probe assay detected only 2 NoV GI genotypes from water samples. Notably, groundwater-borne NoV GI strains detected by the improved JJV1PM-probe assay were associated with groundwater-borne AGE outbreaks in South Korea. The results of this study underscore the importance of the evaluation of RT-qPCR assays using recently circulating NoV strains prior to field application.

Can Use of Viral Load Improve Norovirus Clinical Diagnosis and Disease Attribution?

BACKGROUND

Real-time reverse-transcriptase polymerase chain reaction (RT-PCR) is the state-of-the-art diagnostic for norovirus. Cycle threshold (Ct), an indicator of viral load, may be associated with symptomatic disease as well as demographic and outbreak characteristics.

METHODS

Data on (1) outbreak and sporadic cases and (2) asymptomatic controls in the United States and Latin America were analyzed. With multivariate regression models, we assessed relationships between various factors and Ct values, and we calculated odds ratios (ORs) for the presence of symptoms and attributable fractions of norovirus. Receiver-operating characteristic analysis was performed to define an optimal Ct cutoff to identify disease-causing infections.

RESULTS

Cycle threshold values were lower (ie, higher viral loads) among symptomatic cases (model-adjusted mean ± standard error: 25.3 ± 1.2) compared with asymptomatic controls (28.5 ± 1.4). Cycle threshold values were significantly different across age groups, norovirus genogroups, timing of specimen collection, outbreak settings, and transmission modes. Genogroup II (GII) Ct values were associated with presence of symptoms (OR = 1.1), allowing us to estimate that 16% of diarrheal disease was attributable to norovirus. The optimized Ct cutoff led to poor sensitivity and specificity for genogroup I and GII.

CONCLUSIONS

Cycle threshold values were associated with host, pathogen, and outbreak factors. Cycle threshold values may not effectively distinguish disease-causing infection for individual patients, but they are useful for epidemiological studies aiming to attribute disease.

Prospects and Challenges in the Development of a Norovirus Vaccine

PURPOSE

Norovirus is the leading cause of acute epidemic gastroenteritis among children under the age of 5 years and adults in the United States and in adults worldwide, accounting for an estimated 20% of episodes of acute gastroenteritis across all ages. No effective vaccine is presently available. This article provides an overview of the current state of norovirus vaccine development, emphasizing barriers and challenges in the development of an effective vaccine, correlates of protection used to assess vaccine efficacy, and the results of clinical trials of the major candidate vaccines.

METHODS

We performed an unstructured literature review of published articles listed in PubMed in the field of norovirus vaccine development, with an emphasis on studies in humans.

FINDINGS

Two candidate vaccines have reached clinical trials, and a number of other candidates are in the preclinical stages of development. Multivalent vaccination may be effective in inducing broadly neutralizing antibodies protective against challenge with novel and heterologous norovirus strains. Most identified correlates of protection have not been validated in large-scale challenge studies, nor have the degrees to which these correlates covary been assessed.

IMPLICATIONS

Immune correlates of protection against norovirus infection need to be further developed to facilitate additional studies of the tolerability and efficacy of candidate norovirus vaccines in humans.

A Luciferase Immunoprecipitation System (LIPS) assay for profiling human norovirus antibodies

A luciferase immunoprecipitation systems (LIPS) assay was developed to define the antigenic specificity and titer of antibodies directed against human norovirus (HuNoV). Recombinant proteins, expressed by plasmid constructs encoding Renilla luciferase (Ruc) fused to the full-length HuNoV major capsid protein (VP1) (Ruc-antigen), were generated for ten HuNoV strains. In addition, subdomain constructs Ruc-Shell (S) and Ruc-Protruding (P) were engineered for a representative GII.4 norovirus (strain GII.4/2006b). The LIPS assay measured antibody levels in a well-defined panel of HuNoV-specific sera, and the results were compared to an ELISA standard. In hyperimmune sera, the LIPS produced titers similar to or higher than those measured by the ELISA of HuNoV-specific antibodies. The specificity of antibodies in various sera was profiled by LIPS with a panel of diverse Ruc-antigens containing full-length HuNoV VP1 proteins or VP1 subdomains, and the assay detected both specific and cross-reactive antibodies. Competition assays, in which antibodies were pre-incubated with one or more intact VLPs representing different genotypes, proved useful in further assessment of the antibody specificity detected by LIPS in complex polyclonal sera. The profiling of HuNoV-specific antibodies in the high-throughput LIPS format may prove useful in defining the strength or specificity of the adaptive immune response following natural infection or vaccination.

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.

Frequency and molecular characterization of human norovirus in Erzurum, Turkey

BACKGROUND/AIM

There are limited studies on genotyping and phylogenetic analysis of norovirus in Turkey, and this has not previously been studied in the Eastern Anatolia region. The aim of the present study was to determine the norovirus profile in this region with genotyping and phylogenetic analysis.

MATERIALS AND METHODS

Included in the study were stool samples obtained from 427 people from different age groups in Eastern Anatolia. The nucleic acid samples isolated by the automatic system and nucleic acid sequence reactions and phylogenetic analyses were performed on RNA samples.

RESULTS

The presence of norovirus was detected in 86 (20.1%) of the 427 stool samples by RT-PCR analysis. Twenty-six samples selected randomly from norovirus-RNA positive samples were subjected to the sequence reaction. In 24 of the 26 samples, genogroup GII was determined, as well as one each from GI and GIV in sequence reactions. Four different genotypes were detected in genogroup GII, which were determined to be the dominant types. These were GII.1, GII.4, GII.16, and GII.21. The GI.6 and GIV.1 genotypes were determined in genogroups GI and GIV, respectively.

CONCLUSION

The high frequency and genetic diversity of these infections are risk factors for disease and so vaccine studies should be undertaken in consideration of this situation.

Genetic Analysis of Norovirus Strains that Caused Gastroenteritis Outbreaks Among River Rafters in the Grand Canyon, Arizona

Toilet solid waste samples collected from five outbreaks among rafters in the Grand Canyon were subjected to sequencing analysis of norovirus partial capsid gene. The results revealed that a GI.3 strain was associated with one outbreak, whereas the other outbreaks were caused by GII.5 whose sequences shared >98.9% homology.

Food-Borne Viruses in Shellfish: Investigation on Norovirus and HAV Presence in Apulia (SE Italy)

Shellfish are an important vehicle for transmission of food-borne pathogens including norovirus (NoV) and hepatitis A virus (HAV). The risks related with consumption of shellfish are greater if these products are eaten raw or slightly cooked. As molluscs are filter-feeding organisms, they are able to concentrate pathogens dispersed in the water. Data on shellfish viral contamination are therefore useful to obtain a background information on the presence of contamination in the environment, chiefly in shellfish production areas and to generate a picture of the epidemiology of viral pathogens in local populations. From January 2013 to July 2015, 253 samples of bivalve molluscs collected in harvesting areas from a large coastal tract (860 km) of Southern Italy were screened for HAV and NoV of genogroups GI and GII, using real-time reverse transcription qualitative PCR. The RNA of HAV was not detected in any of the analyzed samples. In contrast, the RNA of NoV was identified in 14.2% of the samples with a higher prevalence of NoVs of genogroup GII (12.2%) than genogroup GI (1.6%). Upon sequence analysis of a short diagnostic region located in capsid region, the NoV strains were characterized as GII.2, GII.4 Sydney 2012, GII.6, GII.13, GI.4, and GI.6, all which were circulating in local populations in the same time span. These data confirm that consumption of mussels can expose consumers to relevant risks of infection. Also, matching between the NoV genotypes circulating in local population and detected in molluscs confirms the diffusion in the environment of NoVs.

Increase in outbreaks of gastroenteritis linked to bathing water in Finland in summer 2014

An increased number of suspected outbreaks of gastroenteritis linked to bathing water were reported to the Finnish food- and waterborne outbreak (FWO) registry in July and August 2014. The investigation reports were assessed by a national outbreak investigation panel. Eight confirmed outbreaks were identified among the 15 suspected outbreaks linked to bathing water that had been reported to the FWO registry. According to the outbreak investigation reports, 1,453 persons fell ill during these outbreaks. Epidemiological and microbiological data revealed noroviruses as the main causative agents. During the outbreaks, exceptionally warm weather had boosted the use of beaches. Six of eight outbreaks occurred at small lakes; for those, the investigation strongly suggested that the beach users were the source of contamination. In one of those eight outbreaks, an external source of contamination was identified and elevated levels of faecal indicator bacteria (FIB) were noted in water. In the remaining outbreaks, FIB analyses were insufficient to describe the hygienic quality of the water. Restrictions against bathing proved effective in controlling the outbreaks. In spring 2015, the National Institute for Health and Welfare (THL) and the National Supervisory Authority for Welfare and Health (Valvira) published guidelines for outbreak control to prevent bathing water outbreaks.

Intranasal delivery of a bivalent norovirus vaccine formulated in an in situ gelling dry powder

The global health community is beginning to understand the burden of norovirus-associated disease, which has a significant impact in both developed and developing countries. Norovirus virus like particle (VLP)-based vaccines are currently under development and have been shown to elicit systemic and mucosal immune responses when delivered intranasally. In the present study, we describe the use of a dry powder formulation (GelVac™) with an in situ gelling polysaccharide (GelSite™) extracted from Aloe vera for nasal delivery of a bivalent vaccine formulation containing both GI and GII.4 norovirus VLPs. Dose-ranging studies were performed to identify the optimal antigen dosages based on systemic and mucosal immune responses in guinea pigs and determine any antigenic interference. A dose-dependent increase in systemic and mucosal immunogenicity against each of the VLPs were observed as well as a boosting effect for each VLP after the second dosing. A total antigen dose of ≥50 μg of each GI and GII.4 VLPs was determined to be the maximally immunogenic dose in guinea pigs. The immunogenicity results of this bivalent formulation, taken together with previous work on monovalent GelVac™ norovirus vaccine formulation, provides a basis for future development of this norovirus VLP vaccine.

Genetic and Epidemiologic Trends of Norovirus Outbreaks in the United States from 2013 to 2016 Demonstrated Emergence of Novel GII.4 Recombinant Viruses

Noroviruses are the most frequent cause of epidemic acute gastroenteritis in the United States. Between September 2013 and August 2016, 2,715 genotyped norovirus outbreaks were submitted to CaliciNet. GII.4 Sydney viruses caused 58% of the outbreaks during these years. A GII.4 Sydney virus with a novel GII.P16 polymerase emerged in November 2015, causing 60% of all GII.4 outbreaks in the 2015-2016 season. Several genotypes detected were associated with more than one polymerase type, including GI.3, GII.2, GII.3, GII.4 Sydney, GII.13, and GII.17, four of which harbored GII.P16 polymerases. GII.P16 polymerase sequences associated with GII.2 and GII.4 Sydney viruses were nearly identical, suggesting common ancestry. Other common genotypes, each causing 5 to 17% of outbreaks in a season, included GI.3, GI.5, GII.2, GII.3, GII.6, GII.13, and GII.17 Kawasaki 308. Acquisition of alternative RNA polymerases by recombination is an important mechanism for norovirus evolution and a phenomenon that was shown to occur more frequently than previously recognized in the United States. Continued molecular surveillance of noroviruses, including typing of both polymerase and capsid genes, is important for monitoring emerging strains in our continued efforts to reduce the overall burden of norovirus disease.

Identification of a novel canine norovirus

By screening a collection of fecal samples from young dogs from different European countries, noroviruses (NoVs) were found in 13/294 (4.4%) animals with signs of enteritis whilst they were not detected in healthy dogs (0/42). An informative portion of the genome (3.4 kb at the 3′ end) was generated for four NoV strains. In the capsid protein VP1 region, strains 63.15/2015/ITA and FD53/2007/ITA were genetically related to the canine GVI.2 strain C33/Viseu/2007/PRT (97.4–98.6% nt and 90.3–98.6% aa). Strain FD210/2007/ITA displayed the highest identity to the GVI.1 canine strain Bari/91/2007/ITA (88.0% nt and 95.0% aa). Strain 5010/2009/ITA displayed only 66.6–67.6% nt and 75.5–81.6% aa identities to the GVI.1 canine strains FD210/2007/ITA and Bari/91/2007/ITA and the GVI feline strain M49-1/2012/JPN. Identity to the other canine/feline NoVs strains in the VP1 was lower than 67.6% nt and 62.7% aa. Based on the full-length VP1 amino acid sequence and the criteria proposed for distinction of NoV genotypes, the canine NoV 5010/2009/ITA could represent the prototype of a third GVI genotype, thus providing further evidence for the genetic heterogeneity of NoVs in carnivores.

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Noroviruses are important human pathogens, also found in several animal species.

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Canine noroviruses were detected in 4.4% (13/294) of diarrhoeic dogs.

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Upon genome sequencing, a novel canine norovirus was identified.

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The observed genetic diversity may pose a challenge for diagnostics.

Environmental Surveillance of Norovirus Genogroups I and II for Sensitive Detection of Epidemic Variants

Sewage samples have been investigated to study the norovirus concentrations in sewage or the genotypes of noroviruses circulating in human populations. However, the statistical relationship between the concentration of the virus and the number of infected individuals and the clinical importance of genotypes or strains detected in sewage are unclear. In this study, we carried out both environmental and clinical surveillance of noroviruses for 3 years, 2013 to 2016. We performed cross-correlation analysis of the concentrations of norovirus GI or GII in sewage samples collected weekly and the reported number of gastroenteritis cases. Norovirus genotypes in sewage were also analyzed by pyrosequencing and compared with those identified in stool samples. The cross-correlation analysis found the peak coefficient (R = 0.51) at a lag of zero, indicating that the variation in the GII concentration, expressed as the log₁₀ number of copies per milliliter, was coincident with that in the gastroenteritis cases. A total of 15 norovirus genotypes and up to 8 genotypes per sample were detected in sewage, which included all of the 13 genotypes identified in the stool samples except 2. GII.4 was most frequently detected in both sample types, followed by GII.17. Phylogenetic analysis revealed that a strain belonging to the GII.17 Kawasaki 2014 lineage had been introduced into the study area in the 2012-2013 season. An increase in GI.3 cases was observed in the 2015-2016 season, and sewage monitoring identified the presence of GI.3 in the previous season (2014-2015). Our results demonstrated that monitoring of noroviruses in sewage is useful for sensitive detection of epidemic variants in human populations.IMPORTANCE We obtained statistical evidence of the relationship between the variation in the norovirus GII concentration in sewage and that of gastroenteritis cases during the 3-year study period. Sewage sample analysis by a pyrosequencing approach enabled us to understand the temporal variation in the norovirus genotypes circulating in human populations. We found that a strain closely related to the GII.17 Kawasaki 2014 lineage had been introduced into the study area at least 1 year before its appearance and identification in clinical cases. A similar pattern was observed for GI.3; cases were reported in the 2015-2016 season, and closely related strains were found in sewage in the previous season. Our observation indicates that monitoring of noroviruses in sewage is useful for the rapid detection of an epidemic and is also sensitive enough to study the molecular epidemiology of noroviruses. Applying this approach to other enteric pathogens in sewage will enhance our understanding of their ecology.

Carbon Dots' Antiviral Functions Against Noroviruses

This study reported the first assessment of carbon dots’ (CDots) antiviral activity to human norovirus virus-like-particles (VLPs), GI.1 and GII.4 VLPs. CDots with different surface passivation molecules, 2,2′-(ethylenedioxy)bis(ethylamine) (EDA)-CDots and 3-ethoxypropylamine (EPA)-CDots, were synthesized and evaluated. The results indicated both EDA- and EPA- CDots were highly effective to inhibit both strains of VLPs’ bindings to histo-blood group antigens (HBGA) receptors on human cells at CDots concentration of 5 µg/mL, with EDA-CDots achieving 100% inhibition and EPA CDots achieving 85–99% inhibition. At low CDots concentration (2 µg/mL), positively charged EDA-CDots exhibited higher inhibitory effect (~82%) than non-charged EPA-CDots (~60%), suggesting the surface charge status of CDots played a role in the interactions between CDots and the negatively charged VLPs. Both types of CDots also exhibited inhibitory effect on VLP’s binding to their respective antibodies, but much less effective than those to HBGA binding. After CDots treatments, VLPs remained intact, and no degradation was observed on VLPs’ capsid proteins. Taken together, the observed antiviral effects of CDots on noroviruses were mainly through the effective inhibition of VLPs’ binding to HBGA receptors and moderate inhibition of VLPs’ binding to their antibodies, without affecting the integrity of viral capsid protein and the viral particle.

The transmissibility of noroviruses: Statistical modeling of outbreak events with known route of transmission in Japan

In Japan, the fraction of norovirus outbreaks attributable to human-to-human transmission has increased with time, and the timing of the increased fraction has coincided with the increase in the observed fraction of genogroup II genotype 4 (GII.4). The present study aimed to estimate the time-dependent changes in the transmissibility of noroviruses. The effective reproduction number (R_y), for year y, was estimated by analyzing the time series surveillance data for outbreak events from 2000 to 2016. R_y was estimated by using the fraction of outbreak events that were attributable to human-to-human transmission and by employing three different statistical models that are considered to mechanistically capture the possible data-generating process in different ways. The R_y estimates ranged from 0.14 to 4.15 in value, revealing an overall increasing trend (p<0.05 for all three models). The proportion of outbreaks caused by GII and GII.4 viruses among the total events also increased with time, and positive correlations were identified between transmissibility and these proportions. Parametric modeling of R_y indicated that the time-dependent patterns of R_y were better described by a step function plus linear trend rather than the step function alone that reflects the widespread use of reverse transcriptase PCR (RT-PCR) in and after 2007 for laboratory diagnosis. Accordingly, we conclude that norovirus transmissibility has increased over the past 16 years in Japan. The change is at least partially explained by the time-dependent domination of the contagious GII genogroup (e.g., GII.4), indicating that noroviruses better fitted to humans have selectively caused the human-to-human transmissions, thereby altering the epidemiology of this pathogen.

Exploration of the metal coordination region of concanavalin A for its interaction with human norovirus

Rapid methods for the detection and clinical treatment of human norovirus (HuNoV) are needed to control foodborne disease outbreaks, but reliable techniques that are fast and sensitive enough to detect small amounts of HuNoV in food and aquatic environments are not yet available. We explore the interactions between HuNoV and concanavalin A (Con A), which could facilitate the development of a sensitive detection tool for HuNoV. Biophysical studies including hydrogen/deuterium exchange (HDX) mass spectrometry and surface plasmon resonance (SPR) revealed that when the metal coordinated region of Con A, which spans Asp16 to His24, is converted to nine alanine residues (mCon A^MCR), the affinity for HuNoV (GII.4) diminishes, demonstrating that this Ca²⁺ and Mn²⁺ coordinated region is responsible for the observed virus-protein interaction. The mutated carbohydrate binding region of Con A (mCon A^CBR) does not affect binding affinity significantly, indicating that MCR of Con A is a major region of interaction to HuNoV (GII.4). The results further contribute to the development of a HuNoV concentration tool, Con A-immobilized polyacrylate beads (Con A-PAB), for rapid detection of genotypes from genogroups I and II (GI and GII). This method offers many advantages over currently available methods, including a short concentration time. HuNov (GI and GII) can be detected in just 15 min with 90% recovery through Con A-PAB application. In addition, this method can be used over a wide range of pH values (pH 3.0 – 10.0). Overall, this rapid and sensitive detection of HuNoV (GI and GII) will aid in the prevention of virus transmission pathways, and the method developed here may have applicability for other foodborne viral infections.

Near Real-Time Surveillance of U.S. Norovirus Outbreaks by the Norovirus Sentinel Testing and Tracking Network - United States, August 2009-July 2015

Norovirus is the leading cause of endemic and epidemic acute gastroenteritis in the United States (1). New variant strains of norovirus GII.4 emerge every 2-4 years (2-4) and are often associated with increased disease and health care visits (5-7). Since 2009, CDC has obtained epidemiologic data on norovirus outbreaks from state health departments through the National Outbreak Reporting System (NORS) (8) and laboratory data through CaliciNet (9). NORS is a web-based platform for reporting waterborne, foodborne, and enteric disease outbreaks of all etiologies, including norovirus, to CDC. CaliciNet, a nationwide electronic surveillance system of local and state public health and regulatory agency laboratories, collects genetic sequences of norovirus strains associated with gastroenteritis outbreaks. Because these two independent reporting systems contain complementary data, integration of NORS and CaliciNet records could provide valuable public health information about norovirus outbreaks. However, reporting lags and inconsistent identification codes in NORS and CaliciNet records have been an obstacle to developing an integrated surveillance system.

Norovirus Disease in Older Adults Living in Long-Term Care Facilities: Strategies for Management

Purpose of Review

Noroviruses are the most common cause of gastroenteritis outbreaks in long-term care facility (LTCFs). This review summarizes the most up-to-date knowledge on norovirus infection in LTCFs with the aim of identifying potential strategies for management.

Recent Findings

LTCF residents are at greater risk of norovirus infection. Early identification of norovirus infection and prompt initiation of appropriate supportive therapy are required to reduce morbidity and mortality. Measures to prevent outbreaks and reduce the risk of norovirus infection in LTCFs include timely diagnosis and implementation of infection control interventions to limit virus transmission.

Summary

Current guidelines for prevention and control are based on generic principles of infection control. Real-time reverse transcription-quantitative polymerase chain reaction assays have been the gold standard for the rapid and sensitive detection of noroviruses. With the recent breakthroughs of human norovirus in vitro culture, doors are now opened to evaluate the efficacy of environmental disinfectants and hand hygiene options. Additionally, development of licensed vaccines against noroviruses may provide another important tool for infection prevention among high-risk individuals.