Explore the vast range of titles available.

Human noroviruses (NoVs) are considered a worldwide leading cause of acute non-bacterial gastroenteritis. Due to a combination of prolonged shedding of high virus levels in feces, virus particle shedding during asymptomatic infections, and a high environmental persistence, NoVs are easily transmitted pathogens. Norovirus (NoV) outbreaks have often been reported and tend to affect a lot of people. NoV is spread via feces and vomit, but this NoV spread can occur through several transmission routes. While person-to-person transmission is without a doubt the dominant transmission route, human infective NoV outbreaks are often initiated by contaminated food or water. Zoonotic transmission of NoV has been investigated, but has thus far not been demonstrated. The presented review aims to give an overview of these NoV transmission routes. Regarding NoV person-to-person transmission, the NoV GII.4 genotype is discussed in the current review as it has been very successful for several decades but reasons for its success have only recently been suggested. Both pre-harvest and post-harvest contamination of food products can lead to NoV food borne illness. Pre-harvest contamination of food products mainly occurs via contact with polluted irrigation water in case of fresh produce or with contaminated harvesting water in case of bivalve molluscan shellfish. On the other hand, an infected food handler is considered as a major cause of post-harvest contamination of food products. Both transmission routes are reviewed by a summary of described NoV food borne outbreaks between 2000 and 2010. A third NoV transmission route occurs via water and the spread of NoV via river water, ground water, and surface water is reviewed. Finally, although zoonotic transmission remains hypothetical, a summary on the bovine and porcine NoV presence observed in animals is given and the presence of human infective NoV in animals is discussed.

Background Noroviruses (NoVs) are an important cause of acute gastroenteritis in humans worldwide. To gain insight into the epidemiologic patterns of NoV outbreaks and to determine the genetic variation of NoVs strains circulating in Belgium, stool samples originating from patients infected with NoVs in foodborne outbreak investigations were analysed between December 2006 and December 2010. Results NoVs were found responsible of 11.8% of all suspected foodborne outbreaks reported in the last 4 years and the number of NoV outbreaks reported increased along the years representing more than 30% of all foodborne outbreaks in 2010. Genogroup II outbreaks largely predominated and represented more than 90% of all outbreaks. Phylogenetic analyses were performed with 63 NoV-positive samples for the partial polymerase (N = 45) and/or capsid gene (N = 35) sequences. For 12 samples, sequences covering the ORF1-ORF2 junction were obtained. A variety of genotypes was found among genogroups I and II; GII.4 was predominant followed in order of importance by GII.2, GII.7, GII.13, GI.4 and GI.7. In the study period, GII.4 NoVs variants 2006a, 2006b, 2007, 2008 and 2010 were identified. Moreover, phylogenetic analyses identified different recombinant NoV strains that were further characterised as intergenotype (GII.e/GII.4 2007, GII.e/GII.3 and GII.g/GII.1) and intersub-genotype (GII.4 2006b/GII.4 2007 and GII.4 2010/GII.4 2010b) recombinants. Conclusions NoVs circulating in the last 4 years in Belgium showed remarkable genetic diversity either by small-scale mutations or genetic recombination. In this period, GII.4 2006b was successfully displaced by the GII.4 2010 subtype, and previously reported epidemic GII.b recombinants seemed to have been superseded by GII.e recombinants in 2009 and GII.g recombinants in 2010. This study showed that the emergence of novel GII.4 variants together with novel GII recombinants could lead to an explosion in NoV outbreaks, likewise to what was observed in 2008 and 2010. Among recombinants detected in this study, two hitherto unreported strains GII.e/GII.3 and GII.g/GII.1 were characterised. Surveillance will remain important to monitor contemporaneously circulating strains in order to adapt preventive and curative strategies.

Two genotypes (Jena and Newbury2) and two intergenotype recombinant strains have been recognized in bovine noroviruses. Several studies have shown an apparent predominance of bovine infection with Newbury2-related (genotype 2) strains. Bovine stool samples were screened with two primer pairs targeting both the polymerase and the capsid genes. Among the predominant genotype 2 sequences, two were genetically related to the recombinant strain Thirsk10. The detection of sequences genetically related to Thirsk10, together with the very low rate of detection of Jena-related sequences, characterized the bovine norovirus population in Belgium, a representative region of continental Europe. Unexpectedly, bovine kobuvirus-related sequences were also amplified, extending their distribution area in Europe.

Porcine noroviruses and sapoviruses belong to the family Caliciviridae and are rarely reported in European countries. In this study, swine stools from a region representative of northern Europe were screened for these viruses by RT-PCR. Both porcine noroviruses and sapoviruses were detected, showing their circulation in this region. The porcine norovirus strains were genetically related to genotype 19 strains in the genogroup II of the genus Norovirus. The porcine sapovirus strains were genetically related to the porcine enteric calicivirus Cowden reference strain and to newly described porcine strains in the genus Sapovirus.

Bovine noroviruses are enteric pathogens that are detected in stool samples from cattle. Five genogroups are currently described in the genus Norovirus (family Caliciviridae), and within the genogroups, sequences are further divided into genotypes according to genetic homology and phylogenetic relationships. In this study, stool specimens from Belgian cattle were screened by RT-PCR. All of the sequences that were detected were phylogenetically related to genogroup III genotype 2 bovine noroviruses, confirming their higher prevalence in comparison with strains from genotype 1. When other sequences from around the world were introduced, phylogenetic inferences allowed neither the determination of phylogenetic lineages over time nor the deduction of topotypes for genotype 2 bovine noroviruses. Three complete genotype 2 bovine norovirus sequences were also compared genetically (Newbury2/1976 /UK, Dumfries/1994/UK and B309/2003/BE). Interestingly, the genetic divergence of the complete genomes of these three strains was relatively low, but a region of the N-terminal protein encoded by ORF1, the hypervariable region of the capsid gene encoded by ORF2, and a region of the minor structural protein encoded by ORF3 seem to be the most exposed to genetic evolution. Bayesian inference also showed that genetic evolution of genogroup III, genotype 2 bovine noroviruses over a 30-year period seemed to be lower than that already reported for noroviruses from the genotypes 3 and 4 in genogroup II.

Les Norovirus (NoV), appartenant à la famille des Caliciviridae, sont une cause majeure d’épidémies et de cas sporadiques de gastroentérites hautement contagieuses chez l’homme. Leur transmission emprunte la voie fécale-orale et ils sont à l'origine d’une part importante des toxi-infections humaines d'origine alimentaire, en particulier dues à la consommation de mollusques bivalves. Ils possèdent un génome constitué d’ARN monocaténaire de polarité positive et sont classeés par analyse de proximité génétique en cinq génogroupes, contenant chacun plusieurs génotypes.Un problème majeur réside dans l’incapacité à multiplier facilement les NoV en culture de cellules. La RT-PCR est devenue la méthode de choix pour leur détection dans les échantillons de matières fécales, les denrées alimentaires et les prélèvements effectués dans l’environnement. Il est important de disposer de techniques à la fois sensibles et permettant également la détection d’un large panel de NoV. La quantification de la charge virale est possible par l’utilisation des techniques de RT-PCR en temps réel et est primordiale pour non seulement déterminer le niveau de contamination d’un prélèvement, mais également pour étudier et caractériser la pathogénie de l’infection à NoV.Des NoV ont été détectés dans diverses espèces animales, dont l’espèce bovine. Ces découvertes ont soulevé d'importantes questions sur une éventuelle transmission zoonotique et l'existence d'un réservoir animal pour les NoV. La caractérisation moléculaire des deux prototypes de NoV bovins, nommément le virus Newbury2 et le virus Jena, a révélé qu'ils étaient génétiquement proches et associés aux NoV humains. Parmi les hypothèses évoquées, les animaux pourraient être soit des porteurs passifs de NoV, soit infectés de manière active par ces virus, responsables dès lors d'une zoonose. Caractériser les NoV circulant chez l’homme et les espèces animales est intéressant dans le but d’étudier leurs voies de transmission et l’éventuel passage inter-espèce de ces virus.Un mécanisme important d'évolution des NoV est la recombinaison, d’un grand intérêt dans l’étude des NoV, générant des modifications du génome viral aboutissant à la création d’un génome « chimère » à partir de deux génomes parentaux différents. Elle crée ainsi de la variation génétique et par là l’émergence de nouveaux virus. En effet, il est bien documenté que la recombinaison se produit souvent parmi les NoV et contribue à la diversité génétique de ces virus ainsi qu’à l’apparition de nouvelles épidémies. La prévalence des souches de NoV recombinants peut être sous-estimée par le fait que la caractérisation des NoV est habituellement basée sur le séquençage partiel du gène de l’ARN polymérase-ARN dépendante uniquement, alors qu’idéalement il faudrait séquencer différentes parties du génome, principalement l’ARN polymérase-ARN dépendante et la protéine de capside, pour identifier de tels virus. Il est important de déterminer précisément l'implication exacte de la recombinaison sur l’évolution des NoV afin de comprendre les mécanismes d’évolution des souches et l'avantage sélectif conféré pour certaines d’entre elles. Etudier ce mécanisme permettra de mieux comprendre l’avantage sélectif observé pour certains NoV et aidera à élucider les voies de transmission des NoV.

Widespread industrial adoption of metal additive manufacturing (AM) requires an in-depth understanding of microstructural evolution during AM. In this study, the effect of process parameters and feature thickness on the microstructures of 316L stainless steel components fabricated by laser powder bed fusion (LPBF) was examined. A standard benchmark geometry developed by the National Institute of Standards and Technology, which contained walls of 0.5, 2.5 and 5.0 mm in thickness, was used. Optical microscopy, finite element analysis, scanning electron microscopy and electron backscatter diffraction revealed dramatic microstructural differences in features of different thickness within the same component. The feature thickness influenced the cooling rate, which in turn impacted the melt pool size, solidification microstructure, grain morphology and density of geometrically necessary dislocations. The relationship between feature size and grain morphology was dependent on the energy input used during LPBF. Such behavior suggested that local manipulation of LPBF process parameters can be employed to achieve microstructural homogeneity within the as-printed stainless steel components.

Antiferromagnets have recently been propelled to the forefront of spintronics by their high potential for revolutionizing memory technologies. For this, understanding the formation and driving mechanisms of the domain structure is paramount. In this work, we investigate the domain structure in a thin-film canted antiferromagnet \\(\\)-Fe\\(_2\\)O\\(_3\\). We find that the internal destressing fields driving the formation of domains do not follow the crystal symmetry of \\(\\)-Fe\\(_2\\)O\\(_3\\), but fluctuate due to substrate clamping. This leads to an overall isotropic distribution of the Néel order with locally varying effective anisotropy in antiferromagnetic thin films. Furthermore, we show that the weak ferromagnetic nature of \\(\\)-Fe\\(_2\\)O\\(_3\\) leads to a qualitatively different dependence on magnetic field compared to collinear antiferromagnets such as NiO. The insights gained from our work serve as a foundation for further studies of electrical and optical manipulation of the domain structure of antiferromagnetic thin films.