Norovirus

Follow-Up of Norovirus Contamination in an Oyster Production Area Linked to Repeated Outbreaks

A production area repeatedly implicated in oyster-related gastroenteritis in France was studied for several months over 2 years. Outbreaks and field samples were analyzed by undertaking triplicate extractions, followed by norovirus (NoV) detection using triplicate wells for genomic amplification. This approach allowed us to demonstrate that some variabilities can be observed for samples with a low level of contamination, but most samples analyzed gave reproducible results. At the first outbreak, implicated oysters were collected at the beginning of the contamination event, which was reflected by the higher NoV levels during the first month of the study. During the second year, NoV concentrations in samples implicated in outbreaks and collected from the production area were similar, confirming the failure of the shellfish depuration process. Contamination was detected mainly during winter-spring months, and a high prevalence of NoV GI contamination was observed. A half-life of 18 days was calculated from NoV concentrations detected in oysters during this study, showing a very slow decrease of the contamination in the production area. Preventing the contamination of coastal waters should be a priority.

Co-infection with coxsackievirus A5 and norovirus GII.4 could have been the trigger of the first episode of severe acute encephalopathy in a six-year-old child with the intermittent form of maple syrup urine disease (MSUD)

In this case study, a co-infection with coxsackievirus A5 (family Picornaviridae) and norovirus GII.4 (family Caliciviridae) was detected by RT-PCR in a faecal sample from a six-year-old girl with symptoms of severe acute encephalopathy subsequently diagnosed as the intermittent form of maple syrup urine disease (MSUD). The two co-infecting viruses, which had been detected previously, appeared to have triggered the underlying metabolic disorder. Here, we describe the genotyping of the viruses, as well as the chronological course, laboratory test results, and clinical presentation of this case, which included recurrent vomiting without diarrhoea, metabolic acidosis, unconsciousness, seizure and circulatory collapse, but with a positive final outcome.

Design, synthesis, and evaluation of a novel series of macrocyclic inhibitors of norovirus 3CL protease

Norovirus infections have a major impact on public health worldwide, yet there is a current dearth of norovirus-specific therapeutics and prophylactics. This report describes the discovery of a novel class of macrocyclic inhibitors of norovirus 3C-like protease, a cysteine protease that is essential for virus replication. SAR, structural, and biochemical studies were carried out to ascertain the effect of structure on pharmacological activity and permeability. Insights gained from these studies have laid a solid foundation for capitalizing on the therapeutic potential of the series of inhibitors described herein.

Occurrence of novel GII.17 and GII.21 norovirus variants in the coastal environment of South Korea in 2015

Human norovirus (HNoV), a positive-sense RNA virus, is the main causative agent of acute viral gastroenteritis. Multiple pandemic variants of the genogroup II genotype 4 (GII.4) of NoV have attracted great attention from researchers worldwide. However, novel variants of GII.17 have been overtaking those pandemic variants in some areas of East Asia. To investigate the environmental occurrence of GII in South Korea, we collected water samples from coastal streams and a neighboring waste water treatment plant in North Jeolla province (in March, July, and December of 2015). Based on capsid gene region C analysis, four different genotypes (GII.4, GII.13, GII.17, and GII.21) were detected, with much higher prevalence of GII.17 than of GII.4. Additional sequence analyses of the ORF1-ORF2 junction and ORF2 from the water samples revealed that the GII.17 sequences in this study were closely related to the novel strains of GII.P17-GII.17, the main causative variants of the 2014-2015 HNoV outbreak in China and Japan. In addition, the GII.P21-GII.21 variants were identified in this study and they had new amino acid sequence variations in the blockade epitopes of the P2 domain. From these results, we present two important findings: 1) the novel GII.P17-GII.17 variants appeared to be predominant in the study area, and 2) new GII.21 variants have emerged in South Korea.

An outbreak of norovirus-associated acute gastroenteritis associated with contaminated barrelled water in many schools in Zhejiang, China

Objectives

More than 900 students and teachers at many schools in Jiaxing city developed acute gastroenteritis in February 2014. An immediate epidemiological investigation was conducted to identify the pathogen, infection sources and route of transmission.

Methods

The probable cases and confirmed cases were defined as students or teachers with diarrhoea or vomiting present since the term began in February 2014. An active search was conducted for undiagnosed cases among students and teachers. Details such as demographic characteristics, gastrointestinal symptoms, and drinking water preference and frequency were collected via a uniform epidemiological questionnaire. A case-control study was implemented, and odds ratios (ORs) and 95% confidence intervals were calculated. Rectal swabs from several patients, food handlers and barrelled water factory workers, as well as water and food samples, were collected to test for potential bacteria and viruses.

Results

A total of 924 cases fit the definition of the probable case, including 8 cases of laboratory-confirmed norovirus infection at 13 schools in Jiaxing city between February 12 and February 21, 2014. The case-control study demonstrated that barrelled water was a risk factor (OR: 20.15, 95% CI: 2.59–156.76) and that bottled water and boiled barrelled water were protective factors (OR: 0.31, 95% CI: 0.13–0.70, and OR: 0.36, 95% CI: 0.16–0.77). A total of 11 rectal samples and 8 barrelled water samples were detected as norovirus-positive, and the genotypes of viral strains were the same (GII). The norovirus that contaminated the barrelled water largely came from the asymptomatic workers.

Conclusions

This acute gastroenteritis outbreak was caused by barrelled water contaminated by norovirus. The outbreak was controlled after stopping the supply of barrelled water. The barrelled water supply in China represents a potential source of acute gastroenteritis outbreaks due to the lack of surveillance and supervision. Therefore, more attention should be paid to this area.

Pathogens of Food Animals: Sources, Characteristics, Human Risk, and Methods of Detection

Pathogens associated with food production (livestock) animals come in many forms causing a multitude of disease for humans. For the purpose of this review, these infectious agents can be divided into three broad categories: those that are associated with bacterial disease, those that are associated with viruses, and those that are parasitic in nature. The goal of this chapter is to provide the reader with an overview of the most common pathogens that cause disease in humans through exposure via the food chain and the consequence of this exposure as well as risk and detection methods. We have also included a collection of unusual pathogens that although rare have still caused disease, and their recognition is warranted in light of emerging and reemerging diseases. These provide the reader an understanding of where the next big outbreak could occur. The influence of the global economy, the movement of people, and food makes understanding production animal-associated disease paramount to being able to address new diseases as they arise.

Discovery and Synthesis of Heterocyclic Carboxamide Derivatives as Potent Anti-norovirus Agents

There is an urgent need for structurally novel anti-norovirus agents. In this study, we describe the synthesis, anti-norovirus activity, and structure-activity relationship (SAR) of a series of heterocyclic carboxamide derivatives. Heterocyclic carboxamide 1 (50% effective concentration (EC50)=37 µM) was identified by our screening campaign using the cytopathic effect reduction assay. Initial SAR studies suggested the importance of halogen substituents on the heterocyclic scaffold and identified 3,5-di-boromo-thiophene derivative 2j (EC50=24 µM) and 4,6-di-fluoro-benzothiazole derivative 3j (EC50=5.6 µM) as more potent inhibitors than 1. Moreover, their hybrid compound, 3,5-di-bromo-thiophen-4,6-di-fluoro-benzothiazole 4b, showed the most potent anti-norovirus activity with a EC50 value of 0.53 µM (70-fold more potent than 1). Further investigation suggested that 4b might inhibit intracellular viral replication or the late stage of viral infection.

Detection of Extremely Low Concentrations of Biological Substances Using Near-Field Illumination

An external force-assisted near-field illumination biosensor (EFA-NI biosensor) detects a target substance that is propelled through an evanescent field by an external force. The target substance is sandwiched between an antibody coupled to a magnetic bead and an antibody coupled to a polystyrene bead. The external force is supplied by a magnetic field. The magnetic bead propels the target substance and the polystyrene bead emits an optical signal. The detection protocol includes only two steps; mixing the sample solution with a detection reagent containing the antibody-coated beads and injecting the sample mixture into a liquid cell. Because the system detects the motion of the beads, the sensor allows detection of trace amounts of target substances without a washing step. The detection capability of the sensor was demonstrated by the detection of norovirus virus-like particles at a concentration of ~40 particles per 100 μl in contaminated water.

Enhanced detection of pathogenic enteric viruses in coastal marine environment by concentration using methacrylate monolithic chromatographic supports paired with quantitative PCR

Currently, around 50% of the world's population lives in towns and cities within 100 km of the coast. Monitoring of viruses that are frequently present in contaminated coastal environments, such as rotavirus (RoV) and norovirus (NoV), which are also the major cause of human viral gastroenteritis, is essential to ensure the safe use of these water bodies. Since exposure to as few as 10-100 particles of RoV or NoV may induce gastrointestinal disease, there is a need to develop a rapid and sensitive diagnostic method for their detection in coastal water samples. In this study, we evaluate the application of methacrylate monolithic chromatographic columns, commercially available as convective interaction media (CIM^®), to concentrate pathogenic enteric viruses from saline water samples prior to virus quantification by one-step reverse transcription quantitative PCR (RT-qPCR). Using RoV and NoV as model enteric viruses, we present our results on the most effective viral concentration conditions from saline water matrices using butyl (C4) hydrophobic interaction monolithic support (CIM^® C4). C4 monolithic columns exhibit a good capacity to bind both RoV and NoV and both viruses can be eluted in a single step. Our protocol using a 1 ml C4 column enables processing of 400 ml saline water samples in less than 60 min and increases the sensitivity of RoV and NoV detection by approximately 50-fold and 10-fold respectively. The protocol was also scaled up using larger capacity 8 ml C4 columns to process 4000 ml of seawater samples with concentration factors of 300-fold for RoV and 40-fold for NoV, without any significant increase in processing time. Furthermore, C4 monolithic columns were adapted for field use in an on-site application of RoV concentration from seawater samples with performance equivalent to that of the reference laboratory setup. Overall, the results from successful deployment of CIM C4 columns for concentration of rotavirus and norovirus in seawater samples reiterate the utility of monolithic supports as efficient, scalable and modular preparative tools for processing environmental water samples to enhance viral detection using molecular methods.

Claudins in viral infection: from entry to spread

Tight junctions are critically important for many physiological functions, including the maintenance of cell polarity, regulation of paracellular permeability, and involvement in signal transduction pathways to regulate integral cellular processes. Furthermore, tight junctions enable epithelial cells to form physical barriers, which act as an innate immune mechanism that can impede viral infection. Viruses, in turn, have evolved mechanisms to exploit tight junction proteins to gain access to cells or spread through tissues in an infected host. Claudin family proteins are integral components of tight junctions and are thought to play crucial roles in regulating their permeability. Claudins have been implicated in the infection process of several medically important human pathogens, including hepatitis C virus, dengue virus, West Nile virus, and human immunodeficiency virus, among others. In this review, we summarize the role of claudins in viral infections and discuss their potential as novel antiviral targets. A better understanding of claudins during viral infection may provide insight into physiological roles of claudins and uncover novel therapeutic antiviral strategies.

Structure-based exploration and exploitation of the S4 subsite of norovirus 3CL protease in the design of potent and permeable inhibitors

Human noroviruses are the primary cause of epidemic and sporadic acute gastroenteritis. The worldwide high morbidity and mortality associated with norovirus infections, particularly among the elderly, immunocompromised patients and children, constitute a serious public health concern. There are currently no approved human vaccines or norovirus-specific small-molecule therapeutics or prophylactics. Norovirus 3CL protease has recently emerged as a potential therapeutic target for the development of anti-norovirus agents. We hypothesized that the S₄ subsite of the enzyme may provide an effective means of designing potent and cell permeable inhibitors of the enzyme. We report herein the structure-guided exploration and exploitation of the S₄ subsite of norovirus 3CL protease in the design and synthesis of effective inhibitors of the protease.

Antiviral effect of theaflavins against caliciviruses

Caliciviruses are contagious pathogens of humans and various animals. They are the most common cause of viral gastroenteritis in humans, and can cause lethal diseases in domestic animals such as cats, rabbits and immunocompromised mice. In this study, we conducted cytopathic effect-based screening of 2080 selected compounds from our in-house library to find antiviral compounds against three culturable caliciviruses: feline calicivirus, murine norovirus (MNV) and porcine sapovirus (PoSaV). We identified active six compounds, of which two compounds, both related to theaflavins, showed broad antiviral activities against all three caliciviruses; three compounds (abamectin, a mixture of avermectin B1a and B1b; avermectin B1a; and (-)-epigallocatechin gallate hydrate) were effective against PoSaV only; and a heterocyclic carboxamide derivative (BFTC) specifically inhibited MNV infectivity in cell cultures. Further studies of the antiviral mechanism and structure-activity relationship of theaflavins suggested the following: (1) theaflavins worked before the viral entry step; (2) the effect of theaflavins was time- and concentration-dependent; and (3) the hydroxyl groups of the benzocycloheptenone ring were probably important for the anti-calicivirus activity of theaflavins. Theaflavins could be used for the calicivirus research, and as potential disinfectants and antiviral reagents to prevent and control calicivirus infections in animals and humans.

Saffold virus, an emerging human cardiovirus

Saffold virus (SAFV) is an emerging human cardiovirus that has been shown to be ubiquitous. Initial studies of SAFV focused on respiratory and gastrointestinal infection; however, it has also recently been associated with diverse clinical symptoms including the endocrine, cardiovascular, and neurological systems. Given the systemic nature of SAFV, and its high prevalence, understanding its pathogenicity and clinical impact is of utmost importance. This comprehensive review highlights and discusses recent developments in epidemiology, human pathogenicity, animal, and molecular studies related to SAFV. It also provides detailed insights into the neuropathogenicity of SAFV. We argue that human studies have been confounded by coinfections and therefore require support from robust molecular and animal research. Thereby, we aim to provide foresight into further research to better understand this emerging virus.

Genetic diversity and phenotypic associations of feline caliciviruses from cats in Switzerland

Feline calicivirus (FCV) is a common viral pathogen in domestic cats worldwide. The variable regions of the capsid (VP1) gene of FCV have one of the highest recorded rates of molecular evolution. Understanding the genetic diversity and phylogeny of FCV is a prerequisite to exploring the epidemiology and pathogenesis of this virus and to the development of efficacious vaccine strategies. In this study, we undertook a nationwide molecular characterization of FCV using for the first time nearly complete capsid (VP1) gene sequences. Sequences from 66 FCV samples were used to investigate the correlation between viral phylogeny and several traits, including geographic origin, signalment, husbandry, FCV vaccination and co-infections. Codon-based nucleotide alignment showed that individual nucleotides and their corresponding amino acid sites were either invariant or highly variable. Using a threshold of 20 % genetic distance in variable region E, FCV samples were grouped into 52 strains, 10 of which comprised two to three samples. Significant associations between FCV phylogeny and host characteristics were found, specifically the pedigree status of the cats, and two well-supported lineages were identified in which the current FCV strain definition was confounded. No correlation between viral genetic distances and geographic distances was evident. The greater resolution of the FCV phylogeny in this study compared to previous studies can be attributed to our use of more conserved regions of the capsid (VP1) gene; nonetheless, our results were still hampered by sequence saturation. The study highlights the need for whole-genome sequences for FCV phylogeny studies.

Complete Genome Sequence of a GII.17 Norovirus Isolated from a Rhesus Monkey in China

The previously silent GII.17 norovirus was found to be the predominant genotype causing major epidemics in China in the 2014–2015 winter epidemic season. We report here the complete genomic sequence of a GII.17 norovirus (mky/GII.17/KM1509/CHN/2015) that infected rhesus monkeys at a monkey farm in southwestern China.

A norovirus detection architecture based on isothermal amplification and expanded genetic systems

Noroviruses are the major cause of global viral gastroenteritis with short incubation times and small inoculums required for infection. This creates a need for a rapid molecular test for norovirus for early diagnosis, in the hope of preventing the spread of the disease. Non-chemists generally use off-the shelf reagents and natural DNA to create such tests, suffering from background noise that comes from adventitious DNA and RNA (collectively xNA) that is abundant in real biological samples, especially feces, a common location for norovirus. Here, we create an assay that combines artificially expanded genetic information systems (AEGIS, which adds nucleotides to the four in standard xNA, pairing orthogonally to A:T and G:C) with loop-mediated isothermal amplification (LAMP) to amplify norovirus RNA at constant temperatures, without the power or instrument requirements of PCR cycling. This assay was then validated using feces contaminated with murine norovirus (MNV). Treating stool samples with ammonia extracts the MNV RNA, which is then amplified in an AEGIS-RT-LAMP where AEGIS segments are incorporated both into an internal LAMP primer and into a molecular beacon stem, the second lowering background signaling noise. This is coupled with RNase H nicking during sample amplification, allowing detection of as few as 10 copies of noroviral RNA in a stool sample, generating a fluorescent signal visible to human eye, all in a closed reaction vessel.

Norovirus shedding among food and healthcare workers exposed to the virus in outbreak settings

BACKGROUND

Noroviruses (NoV) are highly contagious and the leading cause of nonbacterial outbreaks of gastroenteritis worldwide. Individuals who are infected asymptomatically may act as reservoirs and facilitate the transmission of NoV, but the likelihood of workers of becoming infected in outbreak settings has not been systematically studied.

OBJECTIVES

We evaluated the occurrence of norovirus infections among workers exposed to the virus in different outbreak settings.

STUDY DESIGN

We screened feces from food handlers and healthcare workers related with gastroenteritis outbreaks, and shedding concentrations over time were calculated from serial samples of infected individuals. Sequence analyses of the capsid P2 domain and region C were used to evaluate linkage between asymptomatic employees and outbreak cases.

RESULTS

Of all employees, 59.1% were positive for NoV, and more than 70% of them were asymptomatic. Asymptomatic infections were significantly more frequent in foodborne compared to person-to-person transmitted outbreaks; and in restaurants and hotels, compared to nursing homes and healthcare institutions. Mean viral loads were similar between symptomatic and asymptomatic individuals, starting at 7.51±1.80 and 6.49±1.93 log10 genome copies/g, respectively, and decreasing to 5.28±0.76 and 4.52±1.45 log10 genome copies/g after 19days.

CONCLUSIONS

The likelihood of becoming infected when a NoV outbreak occurs at the work place is high and similar between food handlers and healthcare workers, but asymptomatic infections are more frequently identified among food handlers. Since shed amounts of viruses in the absence of symptoms are also high, reinforcement of hygiene practices among workers is especially relevant to reduce the risk of virus secondary transmissions.

Multiplexed Molecular Diagnostics for Respiratory, Gastrointestinal, and Central Nervous System Infections

The development and implementation of highly multiplexed molecular diagnostic tests have allowed clinical microbiology laboratories to more rapidly and sensitively detect a variety of pathogens directly in clinical specimens. Current US Food and Drug Administration-approved multiplex panels target multiple different organisms simultaneously and can identify the most common pathogens implicated in respiratory viral, gastrointestinal, or central nervous system infections. This review summarizes the test characteristics of available assays, highlights the advantages and limitations of multiplex technology for infectious diseases, and discusses potential utilization of these new tests in clinical practice.

Detection of human norovirus in intestinal biopsies from immunocompromised transplant patients

Human noroviruses (HuNoVs) can often cause chronic infections in solid organ and haematopoietic stem cell transplant (HSCT) patients. Based on histopathological changes observed during HuNoV infections, the intestine is the presumed site of virus replication in patients; however, the cell types infected by HuNoVs remain unknown. The objective of this study was to characterize histopathological changes during HuNoV infection and to determine the cell types that may be permissive for HuNoV replication in transplant patients. We analysed biopsies from HuNoV-infected and non-infected (control) transplant patients to assess histopathological changes in conjunction with detection of HuNoV antigens to identify the infected cell types. HuNoV infection in immunocompromised patients was associated with histopathological changes such as disorganization and flattening of the intestinal epithelium. The HuNoV major capsid protein, VP1, was detected in all segments of the small intestine, in areas of biopsies that showed histopathological changes. Specifically, VP1 was detected in enterocytes, macrophages, T cells and dendritic cells. HuNoV replication was investigated by detecting the non-structural proteins, RdRp and VPg. We detected RdRp and VPg along with VP1 in duodenal and jejunal enterocytes. These results provide critical insights into histological changes due to HuNoV infection in immunocompromised patients and propose human enterocytes as a physiologically relevant cell type for HuNoV cultivation.

Approved Antiviral Drugs over the Past 50 Years

Since the first antiviral drug, idoxuridine, was approved in 1963, 90 antiviral drugs categorized into 13 functional groups have been formally approved for the treatment of the following 9 human infectious diseases: (i) HIV infections (protease inhibitors, integrase inhibitors, entry inhibitors, nucleoside reverse transcriptase inhibitors, nonnucleoside reverse transcriptase inhibitors, and acyclic nucleoside phosphonate analogues), (ii) hepatitis B virus (HBV) infections (lamivudine, interferons, nucleoside analogues, and acyclic nucleoside phosphonate analogues), (iii) hepatitis C virus (HCV) infections (ribavirin, interferons, NS3/4A protease inhibitors, NS5A inhibitors, and NS5B polymerase inhibitors), (iv) herpesvirus infections (5-substituted 2'-deoxyuridine analogues, entry inhibitors, nucleoside analogues, pyrophosphate analogues, and acyclic guanosine analogues), (v) influenza virus infections (ribavirin, matrix 2 protein inhibitors, RNA polymerase inhibitors, and neuraminidase inhibitors), (vi) human cytomegalovirus infections (acyclic guanosine analogues, acyclic nucleoside phosphonate analogues, pyrophosphate analogues, and oligonucleotides), (vii) varicella-zoster virus infections (acyclic guanosine analogues, nucleoside analogues, 5-substituted 2'-deoxyuridine analogues, and antibodies), (viii) respiratory syncytial virus infections (ribavirin and antibodies), and (ix) external anogenital warts caused by human papillomavirus infections (imiquimod, sinecatechins, and podofilox). Here, we present for the first time a comprehensive overview of antiviral drugs approved over the past 50 years, shedding light on the development of effective antiviral treatments against current and emerging infectious diseases worldwide.

Anti-infective Activity of 2-Cyano-3-Acrylamide Inhibitors with Improved Drug-Like Properties against Two Intracellular Pathogens

Due to the rise of antibiotic resistance and the small number of effective antiviral drugs, new approaches for treating infectious diseases are urgently needed. Identifying targets for host-based therapies represents an emerging strategy for drug discovery. The ubiquitin-proteasome system is a central mode of signaling in the eukaryotic cell and may be a promising target for therapies that bolster the host's ability to control infection. Deubiquitinase (DUB) enzymes are key regulators of the host inflammatory response, and we previously demonstrated that a selective DUB inhibitor and its derivative promote anti-infective activities in host cells. To find compounds with anti-infective efficacy but improved toxicity profiles, we tested a library of predominantly 2-cyano-3-acrylamide small-molecule DUB inhibitors for anti-infective activity in macrophages against two intracellular pathogens: murine norovirus (MNV) and Listeria monocytogenes We identified compound C6, which inhibited DUB activity in human and murine cells and reduced intracellular replication of both pathogens with minimal toxicity in cell culture. Treatment with C6 did not significantly affect the ability of macrophages to internalize virus, suggesting that the anti-infective activity interferes with postentry stages of the MNV life cycle. Metabolic stability and pharmacokinetic assays showed that C6 has a half-life in mouse liver microsomes of ∼20 min and has a half-life of approximately 4 h in mice when administered intravenously. Our results provide a framework for targeting the host ubiquitin system in the development of host-based therapies for infectious disease. Compound C6 represents a promising tool with which to elucidate the role of DUBs in the macrophage response to infection.

An ultrasensitive SiO2-encapsulated alloyed CdZnSeS quantum dot-molecular beacon nanobiosensor for norovirus

Ultrasensitive, rapid and selective diagnostic probes are urgently needed to overcome the limitations of traditional probes for norovirus (NV). Here, we report the detection of NV genogroup II via nucleic acid hybridization technology using a quantum dot (QD)-conjugated molecular beacon (MB) probe. To boost the sensitivity of the MB assay system, an ultrasensitive QD fluorophore with unique optical properties was synthesized, characterized and exploited as a fluorescence signal generator. Alloyed thioglycolic (TGA)-capped CdZnSeS QDs with a high photoluminescence (PL) quantum yield (QY) value of 92% were synthesized, and a modified silanization method was employed to encapsulate the thiol-capped QDs in a silica layer. The resulting highly luminescent alloyed SiO2-coated CdZnSeS QDs had a remarkable PL QY value of 98%. Transmission electron microscopy and dynamic light scattering confirmed the monodispersity of the alloyed nanocrystals, and zeta potential analysis confirmed their colloidal stability. Powder X-ray diffraction and PL lifetime measurements confirmed the surface modification of the QDs. The alloyed TGA-capped and SiO2-coated CdZnSeS QD-conjugated MB bioprobes detected extremely low concentrations of NV RNA. Ultrasensitive detection of low concentrations of NV RNA with a limit of detection (LOD) of 8.2copies/mL in human serum and a LOD of 9.3 copies/mL in buffer was achieved using the SiO2-coated CdZnSeS QD-MB probes, an increase in sensitivity of 3-fold compared with the detection limit for NV RNA using TGA-capped CdZnSeS QD-MBs. The additional merits of our detection system are rapidity, specificity and improved sensitivity over conventional molecular test probes.

Laboratory-based strategy using a new marketed polymerase chain reaction assay to manage diarrheic episodes among patients from rehabilitation and long-term care facilities

Management of Norovirus and Clostridium difficile gastroenteritis is challenging for rehabilitation and long-term care facilities. We evaluated the contribution of a 2-step laboratory-based strategy, including a new ready-to-use Norovirus polymerase chain reaction assay to promote isolation precautions. C difficile and Norovirus were successively identified from 17% and 23% of 52 episodes of diarrhea, respectively, during the winter season, leading to 100% adequate isolation measures. In patient populations with numerous risk factors for diarrhea, a combined laboratory-based approach could improve infection control.

Reduced Diagnostic Performance of Two Norovirus Antigen Enzyme Immunoassays for the Emergent Genogroup II Genotype 17 Kawasaki 2014 Variant

Two commonly used norovirus enzyme immunoassays have reduced diagnostic performance, with clinical sensitivities ranging from 11% to 35% for the detection of the recently emerging genogroup II genotype 17 (GII.17) Kawasaki 2014 variant that caused the majority of infections in Asia during the winter of 2014 to 2015. False-negative results can compromise infection control and patient management.

Acceptability of temporary suspension of visiting during norovirus outbreaks: investigating patient, visitor and public opinion

BACKGROUND

Noroviruses are a leading cause of outbreaks globally and the most common cause of service disruption due to ward closures. Temporary suspension of visiting (TSV) is increasingly a recommended public health measure to reduce exposure, transmission and impact during norovirus outbreaks; however, preventing patient-visitor contact may contravene the ethos of person-centred care, and public acceptability of this measure is not known.

AIM

To investigate the acceptability of TSV during norovirus outbreaks from the perspectives of patients, visitors and the wider public.

METHODS

Cross-sectional survey of patients (N = 153), visitors (N = 175) and the public (N = 224) in three diverse areas in Scotland. Health Belief Model constructs were applied to understand ratings of acceptability of TSV during norovirus outbreaks, and to determine associations between these levels and various predictor variables.

FINDINGS

The majority (84.6%) of respondents indicated that the possible benefits of TSV are greater than the possible disadvantages. Conversely, the majority (70%) of respondents disagreed that TSV 'is wrong as it ignores people's rights to have contact with family and friends'. The majority (81.6%) of respondents agreed that TSV would be more acceptable if exceptions were made for seriously ill or dying patients. Correlational analysis demonstrated that overall acceptability was positively related to perceived severity (r = 0.65), identified benefits (r = 0.54) and implementing additional communication strategies (r = 0.60); acceptability was negatively related to potential barriers (r = -0.49).

CONCLUSIONS

There is greater service user and public support for the use of TSV than concerns around impinging upon patients' rights to have visitors. TSV should be considered as an acceptable infection control measure that could be implemented consistently during norovirus outbreaks.

Bacterial histo-blood group antigens contributing to genotype-dependent removal of human noroviruses with a microfiltration membrane

We demonstrated the genotype-dependent removal of human norovirus particles with a microfiltration (MF) membrane in the presence of bacteria bearing histo-blood group antigens (HBGAs). Three genotypes (GII.3, GII.4, and GII.6) of norovirus-like particles (NoVLPs) were mixed with three bacterial strains (Enterobacter sp. SENG-6, Escherichia coli O86:K61:B7, and Staphylococcus epidermidis), respectively, and the mixture was filtered with an MF membrane having a nominal pore size of 0.45 μm. All NoVLP genotypes were rejected by the MF membrane in the presence of Enterobacter sp. SENG-6, which excreted HBGAs as extracellular polymeric substances (EPS). This MF membrane removal of NoVLPs was not significant when EPS was removed from cells of Enterobacter sp. SENG-6. GII.6 NoVLP was not rejected with the MF membrane in the presence of E. coli O86:K61:B7, but the removal of EPS of E. coli O86:K61:B7 increased the removal efficiency due to the interaction of NoVLPs with the exposed B-antigen in lipopolysaccharide (LPS) of E. coli O86:K61:B7. No MF membrane removal of all three genotypes was observed when S. epidermidis, an HBGA-negative strain, was mixed with NoVLPs. These results demonstrate that the location of HBGAs on bacterial cells is an important factor in determining the genotype-dependent removal efficiency of norovirus particles with the MF membrane. The presence of HBGAs in mixed liquor suspended solids from a membrane bioreactor (MBR) pilot plant was confirmed by immune-transmission electron microscopy, which implies that bacterial HBGAs can contribute to the genotype-dependent removal of human noroviruses with MBR using MF membrane.

Three-dimensional paper-based slip device for one-step point-of-care testing

In this study, we developed a new type of paper-based analytical device (PAD), the three-dimensional (3D) slip-PAD, to detect infectious human norovirus for global healthcare. The 3D configuration of the papers combined with a slip design provides unique features and versatility that overcome the limitations of fluidic manipulation and sensitivity in point-of-care (POC) tests. The assay can be carried out in a single step based on a moveable slip design, making it suitable for unskilled users. The 3D fluidic network developed by layered construction of wax-patterned papers provides different fluidic paths for the sequential delivery of multiple fluids without the need for peripheral equipment. The release and mixing of enhancement reagents on the device improved the sensitivity and detection limit. The assay results could be visualized by naked eye within 10 min, with subsequent amplification of the signal over time (<60 min). The device showed a broad dynamic range of detection and high sensitivity, with a detection limit of 9.5 × 10⁴ copies ml⁻¹ for human norovirus. These results demonstrate that the 3D slip-PAD is a sensitive diagnostic assay for detecting human norovirus infection that is particularly suitable for POC testing in regions where resources are scarce.

An outbreak of norovirus gastroenteritis associated with asymptomatic food handlers in Kinmen, Taiwan

BACKGROUND

In February 2015 an outbreak of gastroenteritis occurred in a distillery in Kinmen, Taiwan. At least 450 affected employees developed the symptoms of diarrhea and vomiting after attending a lunch banquet on 6 February. Epidemiological, laboratory and environmental investigations were conducted to identify the agent and source of this outbreak.

METHODS

A case-control study was carried out among lunch attendees from the distillery. Using a semi-structured questionnaire, food and beverage consumption in the lunch banquet was assessed, as well as demographic and clinical data of the exposed people. An outbreak case was defined as a diner who developed at least three following symptoms: diarrhea, vomiting, abdominal pain, nausea, chills and/or weakness in the 72 h following the lunch. Controls were defined as lunch attendees who did not have any of the above symptoms. Rectal swabs or stool samples of the symptomatic exposed diners and food handlers as well as food and environmental samples were collected to test potential bacteria and viruses. Norovirus was detected by reverse transcription-polymerase chain reaction and sequence analysis. An environmental assessment, including environmental inspection of the restaurant and a review of work practices of food workers, was undertaken.

RESULTS

Of 363 respondents with complete data, 169 met the case definition and 111 met the control definition. Consumption of pork liver in cold appetizers (adjusted odd ratio (aOR) 3.23; 95 % confidence interval (CI): 1.26-8.30) and lamb chops (aOR: 3.98, 95 % CI: 1.74-9.11) were each associated with increased risk of illness. No cases but two asymptomatic food handlers who prepared or cooked the implicated foods tested positive for norovirus genotype I.6. Food and environmental samples were negative for any bacteria. Environmental assessment indicated that hand washing facilities were not properly accessible to food handlers. Inappropriate hygiene practices in food handlers may have contributed to food contamination.

CONCLUSION

Our investigation suggests that etiological agent of this outbreak was norovirus. The food vehicles were pork liver and lamb chops, which may have been contaminated by asymptomatic infected food handlers. Strict adherence to hand hygiene practices and access to hand washing facilities should be reinforced to prevent such foodborne outbreaks.

Current tools for norovirus drug discovery

INTRODUCTION

Rapid transmission of norovirus often occurs due to its low infectious dosage, high genetic diversity and its short incubation time. The viruses cause acute gastroenteritis and may lead to death. Presently, no effective vaccine or selective drugs accepted by the United States Food and Drug Administration (FDA) are available for the treatment of norovirus. Advances in the development of norovirus replicon cell lines, GII.4-Sydney HuNoV strain human B cells, and murine and gnotobiotic pig norovirus models have facilitated the discovery of effective small molecule inhibitors in vitro and in vivo.

AREAS COVERED

This review gives a brief discussion of the biology and replication of norovirus before highlighting the discovery of anti-norovirus molecules. The article coverage includes: an overview of the current state of norovirus drug discovery, the targeting of the norovirus life cycle, the inhibition of structural and nonstructural proteins of norovirus such as proteases and polymerase, and the blockage of virus entry into host cells. Finally, anti-norovirus drugs in the clinical development stage are described.

EXPERT OPINION

The current approach for the counteraction of norovirus focuses on the inhibition of viral RNA polymerase, norovirus 3C-like protease and the structural proteins VP1 as well as the blockade of norovirus entry. Broad-spectrum anti-norovirus molecules, based on the inhibition of 3C-like protease, have been developed. Other host factors and ways to overcome the development of resistance through mutation are also being examined. A dual approach in targeting viral and host factors may lead to an effective counteraction of norovirus infection. Current successes in developing norovirus replicon harboring cells and norovirus infected human cells, as well as murine norovirus models and other animal models such as piglets have facilitated the discovery of effective drugs and helped our understanding of its mechanism of action.

Emerging infectious diseases: Focus on infection control issues for novel coronaviruses (Severe Acute Respiratory Syndrome-CoV and Middle East Respiratory Syndrome-CoV), hemorrhagic fever viruses (Lassa and Ebola), and highly pathogenic avian influenza viruses, A(H5N1) and A(H7N9)

Over the past several decades, we have witnessed the emergence of many new infectious agents, some of which are major public threats. New and emerging infectious diseases which are both transmissible from patient-to-patient and virulent with a high mortality include novel coronaviruses (SARS-CoV, MERS-CV), hemorrhagic fever viruses (Lassa, Ebola), and highly pathogenic avian influenza A viruses, A(H5N1) and A(H7N9). All healthcare facilities need to have policies and plans in place for early identification of patients with a highly communicable diseases which are highly virulent, ability to immediately isolate such patients, and provide proper management (e.g., training and availability of personal protective equipment) to prevent transmission to healthcare personnel, other patients and visitors to the healthcare facility.

A Review of State Licensing Regulations to Determine Alignment with Best Practices to Prevent Human Norovirus Infections in Child-Care Centers

OBJECTIVES

Close, frequent contact between children and care providers in child-care centers presents many opportunities to spread human noroviruses. We compared state licensing regulations for child-care centers with national guidelines written to prevent human noroviruses.

METHODS

We reviewed child-care licensing regulations for all 50 U.S. states and the District of Columbia in effect in June 2015 to determine if these regulations fully, partially, or did not address 14 prevention practices in four topic areas: (1) hand hygiene, (2) exclusion of ill people, (3) environmental sanitation, and (4) diapering.

RESULTS

Approximately two-thirds (8.9) of the 14 practices across all state regulations were partially or fully addressed, with few (2.6) fully addressed. Practices related to exclusion of ill people and diapering were fully addressed most often, while practices related to hand hygiene and environmental sanitation were fully addressed least often.

CONCLUSION

Regulations based on guidelines for best practices are one way to prevent the spread of human noroviruses in child-care facilities, if the regulations are enforced. Our findings show that, in mid-2015, many state child-care regulations did not fully address these guidelines, suggesting the need to review these regulations to be sure they are based on best practices.

Norovirus in Transplantation

Noroviruses are among the most common cause of diarrhea in transplant recipients. The clinical spectrum of norovirus infection after transplant is increasingly being recognized. As substantial morbidity is now associated with norovirus infections in this population; the quest for rapid diagnostic modalities and newer therapies has expanded. Transplant recipients with norovirus infection are at risk for several complications, including protracted illness with malnutrition, organ failure, and chronic viral shedding. This review summarizes the current knowledge on the epidemiology, complications, diagnosis, and treatment of norovirus infection in the transplant setting.

Structure-based design and synthesis of triazole-based macrocyclic inhibitors of norovirus protease: Structural, biochemical, spectroscopic, and antiviral studies

Outbreaks of acute gastroenteritis caused by noroviruses constitute a public health concern worldwide. To date, there are no approved drugs or vaccines for the management and prophylaxis of norovirus infections. A potentially effective strategy for the development of norovirus therapeutics entails the discovery of inhibitors of norovirus 3CL protease, an enzyme essential for noroviral replication. We describe herein the structure-based design of the first class of permeable, triazole-based macrocyclic inhibitors of norovirus 3C-like protease, as well as pertinent X-ray crystallographic, biochemical, spectroscopic, and antiviral studies.

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Novel triazole-based macrocyclic inhibitors of norovirus 3CL protease were synthesized.

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The interplay of conformation and activity was probed using NMR and X-ray crystallography.

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Bound inhibitors assume a β-strand conformation according to X-ray crystal structure.

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Loss of critical hydrogen bonding interactions was revealed by X-ray crystallography.

Human norovirus hyper-mutation revealed by ultra-deep sequencing

Human noroviruses (NoVs) are a major cause of gastroenteritis worldwide. It is thought that, similar to other RNA viruses, high mutation rates allow NoVs to evolve fast and to undergo rapid immune escape at the population level. However, the rate and spectrum of spontaneous mutations of human NoVs have not been quantified previously. Here, we analyzed the intra-patient diversity of the NoV capsid by carrying out RT-PCR and ultra-deep sequencing with 100,000-fold coverage of 16 stool samples from symptomatic patients. This revealed the presence of low-frequency sequences carrying large numbers of U-to-C or A-to-G base transitions, suggesting a role for hyper-mutation in NoV diversity. To more directly test for hyper-mutation, we performed transfection assays in which the production of mutations was restricted to a single cell infection cycle. This confirmed the presence of sequences with multiple U-to-C/A-to-G transitions, and suggested that hyper-mutation contributed a large fraction of the total NoV spontaneous mutation rate. The type of changes produced and their sequence context are compatible with ADAR-mediated editing of the viral RNA.

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Norovirus U-to-C hyper-mutants are present in patient samples.

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Analysis of hyper-mutants in cell culture suggests ADAR-mediated RNA edition.

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Hyper-mutation may contribute to norovirus diversity and evolution.

Foodborne viruses

Among the wide variety of viral agents liable to be found as food contaminants, noroviruses and hepatitis A virus are responsible for most well characterized foodborne virus outbreaks. Additionally, hepatitis E virus has emerged as a potential zoonotic threat. Molecular methods, including an ISO standard, are available for norovirus and hepatitis A virus detection in foodstuffs, although the significance of genome copy detection with regard to the associated health risk is yet to be determined through viability assays. More precise and rapid methods for early foodborne outbreak investigation are being developed and they will need to be validated versus the ISO standard. In addition, protocols for next-generation sequencing characterization of outbreak-related samples must be developed, harmonized and validated as well.

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.

Noroviruses on surfaces: detection, persistence, disinfection and role in environmental transmission

Human noroviruses (HuNoVs), the most common cause of infectious nonbacterial gastroenteritis and the cause of numerous foodborne and hospital outbreaks, are easily transmitted from person-to-person. HuNoVs may persist on surfaces for long periods of time and may be transferred via hands, foods, fomites and air. In this review, studies on methods for detecting HuNoVs on environmental surfaces, such as swabbing, are presented. The review also focuses on recent studies on the efficiency of disinfectants for inactivating HuNoV or its surrogates, such as murine norovirus, on environmental surfaces and hands. Although HuNoV is probably more resistant than MuNoV, this study data adds to the understanding of HuNoV transmission routes and selection of tools for the prevention of HuNoV gastroenteritis outbreaks.

Viruses Causing Gastroenteritis: The Known, The New and Those Beyond

The list of recently discovered gastrointestinal viruses is expanding rapidly. Whether these agents are actually involved in a disease such as diarrhea is the essential question, yet difficult to answer. In this review a summary of all viruses found in diarrhea is presented, together with the current knowledge about their connection to disease.

Oxadiazole-Based Cell Permeable Macrocyclic Transition State Inhibitors of Norovirus 3CL Protease

Human noroviruses are the primary causative agents of acute gastroenteritis and a pressing public health burden worldwide. There are currently no vaccines or small molecule therapeutics available for the treatment or prophylaxis of norovirus infections. Norovirus 3CL protease plays a vital role in viral replication by generating structural and nonstructural proteins via the cleavage of the viral polyprotein. Thus, molecules that inhibit the viral protease may have potential therapeutic value. We describe herein the structure-based design, synthesis, and in vitro and cell-based evaluation of the first class of oxadiazole-based, permeable macrocyclic inhibitors of norovirus 3CL protease.