Article

A Review of Known and Hypothetical Transmission Routes for Noroviruses

Department of Infectious and Parasitic diseases, Virology and Viral diseases, Faculty of Veterinary Medicine, University of Liège, Boulevard du Colonster 20, 4000, Liège, Belgium.
Food and Environmental Virology (Impact Factor: 1.98). 12/2012; 4(4):131-52. DOI: 10.1007/s12560-012-9091-z
Source: PubMed

ABSTRACT 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.

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    • "Various food products such as bivalve mollusks (especially oysters) (Le Guyader et al., 2010; Thebault et al., 2013), fresh fruit and vegetables including different types of lettuce, onions, berries and, more recently, semidried tomatoes have been involved in foodborne disease outbreaks (Bernard et al., 2014; Ethelberg et al., 2010; Fournet et al., 2012; Gallot et al., 2011; Sarvikivi et al., 2012). Fruits and vegetables can be contaminated either at the pre-harvest stage through contact with fecally contaminated irrigation water or during harvesting, packaging, processing, or cooking due to poor hand sanitation (Bitler et al., 2013; Kotwal and Cannon, 2014; Mathijs et al., 2012; Rodriguez-Lazaro et al., 2012). Most foodborne viruses are difficult or currently impossible to cultivate (Hamza et al., 2011) and sensitive molecular methods are therefore used to detect them in food and environmental samples. "
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    ABSTRACT: Noroviruses (genogroup I (NoV GI) and genogroup II (NoV GII)) and the hepatitis A virus (HAV) are frequently involved in foodborne infections worldwide. They are mainly transmitted via the fecal-oral route, direct person-to-person contact or consumption of contaminated water and foods. In food virology, detection methods are currently based on identifying viral genomes using real-time reverse transcriptase PCR (RT-qPCR). One of the general requirements for detecting these viruses in food involves the use of a process control virus to monitor the quality of the entire viral extraction procedure as described in the ISO/TS 15216-1 and 15216-2 standards published in 2013. The selected process control virus should have similar morphological and physicochemical properties as the screened pathogenic virus and thus have the potential to provide comparable extraction efficiency. The aim of this study was to determine which virus should be used for process control, murine norovirus (MNV-1) or Mengovirus, when testing for the presence of HAV, NoV GI and NoV GII in bottled water, lettuce and semi-dried tomatoes. Food samples were spiked with HAV, NoV GI or NoV GII alone or in the presence of MNV-1 or Mengovirus. Recovery rates of each pathogenic virus were compared to those of both process control viruses using a multiple comparison procedure. Neither process control virus influenced the recovery of pathogenic virus regardless of the type of food matrix. MNV-1 was the most appropriate virus for validating the detection of HAV and NoV GII in all three food matrices as well as NoV GI in lettuce. Mengovirus proved to be the most appropriate control for NoV GI detection in bottled water and semi-dried tomatoes. The process control virus is essential for validating viral detection in food and the choice of virus depends on food type and the screened pathogenic virus. Copyright © 2015 Elsevier B.V. All rights reserved.
    International Journal of Food Microbiology 02/2015; 202:57-65. DOI:10.1016/j.ijfoodmicro.2015.02.029 · 3.16 Impact Factor
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    ABSTRACT: Background. Noroviruses are a highly transmissible and a major cause of nosocomial gastroenteritis resulting in bed and hospital-ward closures. Where hospital outbreaks are suspected, it is important to determine the routes of spread so that appropriate infection control procedures can be implemented. To investigate a cluster of norovirus cases occurring in bone marrow transplant children, we undertook norovirus genome sequencing by next generation methods. Detailed comparison of sequence data from two linked cases enabled us to identify the likely direction of spread. Methods. Norovirus cDNA was amplified by overlapping PCR from 13 stool samples from five diagnostic rtPCR positive patients. The amplicons were sequenced by Roche 454, the genomes assembled by de novo assembly and the data analysed phylogenetically. Results. Phylogenetic analysis indicated that patients were infected by viruses similar to four distinct GII.4 subtypes and two patients were linked by the same virus. Of the 14 sites at which there were differences between the consensus sequences of the two linked viral genomes, nine had minor variants present within one or other patient. Further analysis confirmed that minor variants at all nine sites in patient B were present as the consensus sequence in patient A. Conclusions. Phylogenetic analysis excluded a common source of infection in this apparent outbreak. Two of three patients on the same ward had closely related viruses, raising the possibility of cross infection despite protective isolation. Analysis of deep sequence data enabled us to establish the likely direction of nosocomial transmission.
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    ABSTRACT: The aim is to describe the epidemiological and laboratory investigation of a nosocomial outbreak of gastroenteritis and the effectiveness of control measures. In April 2011, an outbreak of gastroenteritis occurred in patients and personnel of the Orthopedic Department of Tzaneio General Hospital, Piraeus, Greece. The hospital infection control committee implemented a series of interventions for the containment of the outbreak. In particular, cases were defined as patients, visitors or hospital personnel with symptoms of vomiting and/or diarrhoea. Clinical and epidemiological information was collected from cases and from all patients hospitalized in the respective department. Investigation for similar cases was made to other hospital departments. Stool samples were submitted to the microbiological laboratory for routine culture, Clostridium difficile toxin assay, and detection of viral antigens. A total of 21 cases were identified; 10 were inpatients, 3 were visitors, and 8 were hospital personnel. All cases had diarrhoea, 6 had vomiting and 1 had fever. Symptoms lasted for 1-3 days and were generally mild. A common food- or water-borne source was not identified. Bacterial stool cultures yielded no enteric pathogen. The antigen immunoassays were positive for norovirus and the diagnosis was confirmed with reverse transcriptase RT-PCR. Instructions for strict hand hygiene and contact precautions were given. Hospital surfaces in the vicinity of the affected patients were cleaned with sodium hypochlorite solution and the rooms were aerated. Visits to the patients were discouraged. The outbreak lasted 10 days with no cases to occur thereafter. All affected staff members were asked to refrain from work until symptom resolution. In conclusion, the reported norovirus outbreak was probably introduced to a hospital department from the community. The prompt response to the outbreak prevented the spread to other hospital departments. Σκοπός της μελέτης ήταν η αναφορά της επιδημιολογικής και εργαστηριακής διερεύνησης συρροής κρουσμάτων γαστρεντερίτιδας στην Ορθοπεδική Κλινική του Γ.Ν.Π. «Τζάνειο», τον Απρίλιο του 2011, καθώς και της αποτελεσματικότητας των μέτρων ελέγχου. Με την παρέμβαση της Επιτροπής Νοσοκομειακών Λοιμώξεων ελήφθησαν άμεσα μέτρα περιορισμού της επιδημίας. Συγκεκριμένα, μελετήθηκαν όλες οι περιπτώσεις ασθενών, συνοδών και προσωπικού με συμπτώματα εμέτου και/ή διάρροιας. Συλλέχθηκαν επιδημιολογικές και κλινικές πληροφορίες από όλους τους νοσηλευόμενους στην κλινική κατά το συγκεκριμένο χρονικό διάστημα και από το προσωπικό. Διερευνήθηκε η ύπαρξη παρόμοιων περιστατικών στα υπόλοιπα νοσηλευτικά τμήματα. Εστάλησαν δείγματα κοπράνων για καλλιέργεια, πραγματοποιήθηκε αναζήτηση ιικών αντιγόνων και τοξίνης Clostridium difficile. Συνολικά προσβλήθηκαν 21 άτομα (10 ασθενείς, 8 μέλη του προσωπικού και 3 συνοδοί ασθενών). Όλοι οι προσβληθέντες εμφάνισαν διαρροϊκές κενώσεις, 6 ανέφεραν και εμέτους, ενώ ένας ασθενής παρουσίασε πυρετό. Η διάρκεια των συμπτωμάτων ήταν 1-3 ημέρες και η βαρύτητα ήταν ήπια. Δεν διαπιστώθηκε προέλευση της επιδημίας από κατανάλωση μολυσμένου τροφίμου ή νερού. Οι καλλιέργειες κοπράνων για εντεροπαθογόνα βακτήρια ήταν αρνητικές. Η αναζήτηση των ιικών αντιγόνων και η μοριακή επιβεβαίωση με RT-PCR ανέδειξαν ως αιτιολογικό παράγοντα τον Norovirus. Έγιναν συστάσεις για αυστηρή εφαρμογή της υγιεινής των χεριών και των προφυλάξεων επαφής. Πραγματοποιήθηκε επιμελής καθαρισμός όλων των επιφανειών που βρίσκονταν στο χώρο των προσβληθέντων με διάλυμα υποχλωριώδους νατρίου και καλός αερισμός των θαλάμων. Περιορίστηκε το επισκεπτήριο και τα προσβεβλημένα άτομα του προσωπικού απείχαν από την εργασία τους έως την πλήρη αποδρομή των συμπτωμάτων. H επιδημία διήρκεσε 10 μέρες και έκτοτε δεν αναφέρθηκαν νέα περιστατικά. Η νοσοκομειακή διασπορά του norovirus πιθανολογείται ότι οφείλεται σε εισαγωγή του ιού από ταυτόχρονη επιδημία στην κοινότητα. Η επιδημιολογική επιτήρηση συνέβαλλε στον άμεσο περιορισμό της επιδημίας.
    Acta Microbiologica Hellenica 07/2013; 58(3):7-11.
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