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Worldwide, noroviruses are a leading cause of gastroenteritis. They can be transmitted from person to person directly or indirectly through contaminated food, water, or environments. To estimate the proportion of foodborne infections caused by noroviruses on a global scale, we used norovirus transmission and genotyping information from multiple international outbreak surveillance systems (Noronet, CaliciNet, EpiSurv) and from a systematic review of peer-reviewed literature. The proportion of outbreaks caused by food was determined by genotype and/or genogroup. Analysis resulted in the following final global profiles: foodborne transmission is attributed to 10% (range 9%-11%) of all genotype GII.4 outbreaks, 27% (25%-30%) of outbreaks caused by all other single genotypes, and 37% (24%-52%) of outbreaks caused by mixtures of GII.4 and other noroviruses. When these profiles are applied to global outbreak surveillance data, results indicate that approximate to 14% of all norovirus outbreaks are attributed to food.

In the winter of 2014/15 a novel GII.P17-GII.17 norovirus strain (GII.17 Kawasaki 2014) emerged, as a major cause of gastroenteritis outbreaks in China and Japan. Since their emergence these novel GII.P17-GII.17 viruses have replaced the previously dominant GII.4 genotype Sydney 2012 variant in some areas in Asia but were only detected in a limited number of cases on other continents. This perspective provides an overview of the available information on GII.17 viruses in order to gain insight in the viral and host characteristics of this norovirus genotype. We further discuss the emergence of this novel GII.P17-GII.17 norovirus in context of current knowledge on the epidemiology of noroviruses. It remains to be seen if the currently dominant norovirus strain GII.4 Sydney 2012 will be replaced in other parts of the world. Nevertheless, the public health community and surveillance systems need to be prepared in case of a potential increase of norovirus activity in the next seasons caused by this novel GII.P17-GII.17 norovirus., Funding Agencies|EU H2020 grant COMPARE [643476]; Virgo Consortium - Dutch government [FES0908]; Hungarian Scientific Research Fund [OTKA/NKFIH K111615]

Noroviruses (NoVs) are responsible for the majority of gastroenteritis outbreaks in humans. Recently, NoV strains which are genetically closely related to human genogroup II (GII) NoVs have been detected in fecal specimens from swine. These findings have raised concern about the possible role of pigs as reservoirs for NoVs that could infect humans. To better understand the epidemiology of swine NoVs in both the swine and the human populations, rapid immunoassays are needed. In this study, baculovirus recombinants were generated to express the capsid gene of a swine NoV GII genotype 11 (GII.11) strain which self-assembled into virus-like particles (VLPs). Subsequently, the purified VLPs were used to evoke monoclonal antibodies (MAbs) in mice. A panel of eight promising MAbs was obtained and evaluated for their ability to bind to heterologous VLPs, denaturated antigens, and truncated capsid proteins. The MAbs could be classified into two groups two MAbs that recognized linear epitopes located at the amino-terminal half (shell domain) of the swine NoV GII.11 VLPs and that cross-reacted with human GII.4 NoV VLPs. The other six MAbs bound to conformational epitopes and did not cross-react with the human GII.4 VLPs. To our knowledge, this is the first report on the characterization of MAbs against swine NoVs. The swine NoV VLPs and the MAbs described here may be further used for the design of diagnostic reagents that could help increase our knowledge of the prevalence of NoV infections in pigs and the possible role of pigs as reservoirs for NoVs. Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Noroviruses (NoVs) are responsible for the majority of gastroenteritis outbreaks in humans. Recently, NoV strains which are genetically closely related to human genogroup II (GII) NoVs have been detected in fecal specimens from swine. These findings have raised concern about the possible role of pigs as reservoirs for NoVs that could infect humans. To better understand the epidemiology of swine NoVs in both the swine and the human populations, rapid immunoassays are needed. In this study, baculovirus recombinants were generated to express the capsid gene of a swine NoV GII genotype 11 (GII.11) strain which self-assembled into virus-like particles (VLPs). Subsequently, the purified VLPs were used to evoke monoclonal antibodies (MAbs) in mice. A panel of eight promising MAbs was obtained and evaluated for their ability to bind to heterologous VLPs, denaturated antigens, and truncated capsid proteins. The MAbs could be classified into two groups: two MAbs that recognized linear epitopes located at the amino-terminal half (shell domain) of the swine NoV GII.11 VLPs and that cross-reacted with human GII.4 NoV VLPs. The other six MAbs bound to conformational epitopes and did not cross-react with the human GII.4 VLPs. To our knowledge, this is the first report on the characterization of MAbs against swine NoVs. The swine NoV VLPs and the MAbs described here may be further used for the design of diagnostic reagents that could help increase our knowledge of the prevalence of NoV infections in pigs and the possible role of pigs as reservoirs for NoVs.

RIVM rapport:In dit rapport worden moleculaire detectiemethoden beschreven voor het aantonen van Norwalk-like calicivirus (NLV) en rotavirus RNA in rioolwaterconcentraten, inclusief de toepassing bij het volgen van explosies van virale gastro-enteritis. Het concentreren van de virussen werd uitgevoerd met behulp van een klassieke filter adsorptie-elutie methode gevolgd door een twee-fase-scheidingsmethode, waarna NLV en rotavirus met behulp van 'reverse transcriptase polymerase chain reaction' (RT-PCR) werden aangetoond. NLV werd aangetroffen in alle rioolwaters die nabij de explosie-locatie bemonsterd werden. Fylogenetische analyse van de nucleotide sequenties van de PCR producten toonde aan dat de in patienten aangetroffen NLV-typen identiek waren aan de typen gevonden in het rioolwater. Bij twee van deze locaties werd ook rotavirus RNA in het rioolwater aangetroffen.NLV werd aangetroffen in 10, en rotavirus in 7 van de 11 vervolgmonsters. Na klonering van de RT-PCR producten werden verschillende typen NLV aangetroffen in 1 monster, wat aangeeft dat er verschillende NLV-typen gelijktijdig kunnen circuleren in Nederland.De hoeveelheid virus in de monsters werd geschat door 10-voudige verdunningen te testen met behulp van RT-PCR. Relatief hoge NLV concentraties werden aangetroffen met maximaal tot de 10-7 verdunning positief voor de aanwezigheid van NLV RNA. Deze resultaten suggereren dat er een potentieel risico is voor wateroverdraagbare transmissie van NLV en rotavirus. Ongeveer 6 maanden na de explosie werd NLV nog steeds aangetroffen in het rioolwater, wat aangeeft dat NLV in het milieu een potentiele besmettingsbron kan zijn. Tevens suggereren deze resultaten dat de ziektelast van NLV en rotavirus in relatie tot gastro-enteritis wel eens hoger zou kunnen zijn in de algemene Nederlandse populatie dan tot nu toe werd aangenomen op basis van de gemelde explosies., In this study we describe a molecular method for the detection of a Norwalk-like virus (NLV) and a rotavirus (RNA) in sewage water concentrates. This includes its application in the monitoring of raw sewage in conjunction with confirmed outbreaks of viral gastro-enteritis. The virus was concentrated from the raw sewage by (conventional) filter adsorption-elution, followed by a two-phase separation. RNA was extracted from the final concentrate through binding to glassbeads. NLV was detected by reverse-transcriptase chain reaction amplification (RT-PCR) in all initial sewage samples collected at locations where an outbreak of gastro-enteritis had been reported. Nucleotide sequence analysis of the PCR products revealed the patient strains and the strains found in the initial sewage samples to be identical. At two of these locations rotavirus was also found in the sewage samples. In addition, NLV was detected by RT-PCR in 10 of the 11 follow-up samples, and rotavirus in 7 of these. After cloning 10 of the NLV-RT-PCR products and nucleotide sequence analysis of 5 clones per sample, 6 out of 10 specimens were found to contain multiple NLV genotypes, indicating co-circulation of several types. The remaining four sewage extracts contained only one genetic type of NLV. The amount of virus in the samples was estimated by testing 10-fold serial dilutions using RT-PCR; this amount was found to be quite variable, with maximum levels as high as 10-7RNA-containing particles per litre. Our findings imply a potential risk in waterborne transmission of NLV and rotavirus. The burden of illness due to NLV or rotavirus is also suggested to be with associated gastro-enteritis in the general population, where it is higher than has been estimated from investigations of outbreaks.

RIVM rapport:In 1996 is een onderzoek gestart naar gastro-enteritis in de huisartsenpraktijk in samenwerking met het Nederlands Instituut voor onderzoek van de Gezondheidszorg (NIVEL). Dit onderzoek heeft tot doel de incidentie van gastro-enteritis in de huisartsenpraktijk te schatten, de effecten van preventieve maateregelen in de veterinaire sector m.b.t. het terugdringen van Salmonella- en Campylobacter-infecties te bepalen, de relatieve bijdrage van een breed panel van micro-organismen in het veroorzaken van gastro-enteritis te bepalen en risicofactoren op te sporen. Het onderzoek bestaat uit een enumeratie-studie en een patient-controleonderzoek. De incidentie van mei 1996 tot mei 1998 werd geschat op 77 huisartsconsulten voor gastro-enteritis per 10.000 persoonjaren. Dit lijkt een lichte daling ten opzichte van de incidentie gevonden in vergelijkbaar onderzoek in 1992-1993 van 90 per 10.000 persoonjaren. De belangrijkste micro-organismen bij gastro-enteritis-patienten waren Campylobacter spp, Salmonella spp, rotavirus, Small Round Structured Viruses (SRSV), Giardia lamblia en Dientamoeba fragilis. Deze laatste twee werden echter ook veel bij controles aangetroffen. De belangrijkste risicofactoren voor gastro-enteritis waren reizen naar Azie (OR=25,8 95%-b.i. 3,0-220,9) en andere ontwikkelingslanden (OR=8,7 95%-b.i. 1,1-70,4) en het hebben van een chronische maagdarmaandoening (OR=6,5 95%-b.i. 3,6-11,4). Voor bacteriele, virale en parasitaire gastro-enteritis werden verschillen in risicofactoren gevonden. De gegevensverzameling van het onderzoek zal in 1999 worden afgerond., In 1996, a study was started on gastroenteritis in collaboration with the Netherlands Institute of Primary Health Care (NIVEL) among gastroentritis patients in care of a general practitioner. This study was aimed at estimating the incidence of gastroenteritis in general practices, evaluating the effects on humans of preventive measures in the veterinary sector to reduce Salmonella and Campylobacter infections, estimating the relative importance of a broad spectrum of micro-organisms causing gastroenteritis and identifying risk factors. The study of gastroenteritis per 10,000 person years consists of an enumeration study and a case control. The incidence from May 1996-May 1998 was estimated at 77 GP consultations. This is slightly lower than the incidence in a comparable study of 90 per 10,000 person years. The most important micro-organisms from 1992-1993 were Campylobacter spp , Salmonella spp, rotavirus, Small Round Structured Viruses (SRSV), Giardia lamblia and Dientamoeba fragilis. However, the latter two were found frequently in controls as well. The most important risk factors for contracting gastroenteritis were travel to Asia (OR=25.8 95% c.i. 3.0-220.9) and other developing countries (OR=8.7 95% c.i.1.1-70.4), and chronic gastrointestinal disorders (OR=6.5 95% c.i. 3.6-11.4). Differences in risk factors were found for bacterial, viral and parasitic gastroenteritis. The data collection will be completed in 1999.

RIVM rapport:In 1996 is een onderzoek gestart naar gastro-enteritis in huisartsenpraktijken. Het onderzoek zal doorgaan tot in 1999. In dit rapport zijn de resultaten van het eerste jaar beschreven. Bij 33 van de 43 peilstations werd een patient-controleonderzoek uitgevoerd. De incidentie van gastro-enteritis, gecorrigeerd voor onvolledigheid van meldingen, was deze 79 per 10.000 personen per jaar. De gecorrigeerde incidentie is vergelijkbaar met de incidentie gemeten in huisartsenpeilstationonderzoek in 1992-1993 van 90 per 10.000 personen per jaar. Het percentage van de patienten waarbij Salmonella kon worden aangetoond (3,5%) was iets lager dan in 1992-1993 (4,4%); het percentage van de patienten waarbij Campylobacter werd gevonden (9,2%) was significant lager dan in 1992-1993 (14,6%). In totaal kon bij 39% van de patienten en bij 22% van de controles een pathogeen worden aangetoond. Dit is een winst van 23% bij patienten ten opzichte van de resultaten bij testen op het standaard diagnostisch pakket. Indien personen die antibiotica hadden gebruikt in de week voor monstername, personen die al meer dan een week klachten hadden en personen van wie het monster langer dan 2 dagen onderweg was geweest, werden uitgesloten was het percentage van de patienten waarbij een pathogeen werd aangetoond 49%. De bevinding dat ook bij 22% van de personen zonder gastro-enteritis een pathogeen werd gevonden, geeft aan dat het aantonen van een pathogeen niet op een causale relatie met gastro-enteritis hoeft te duiden en onderstreept het belang om in dergelijk onderzoek controles te betrekken., In 1996 a physician-based Sentinel-study was started to study the incidence of gastroenteritis and associated pathogens, to identify risk factors and to estimate the disease burden. The study is to be continued until 1999. The Sentinel practitioners enumerate all patients that consult them with gastroenteritis, and in 33 of the 43 Sentinel practices a case-control study is conducted. Results from the first year are published in this report. The incidence of gastroenteritis corrected for incompleteness of the enumeration was 79 per 10,000 person years. This is comparable with the incidence of 90 per 10,000 person years found in a similar study in 1992-1993. Salmonella was found in 3.5% of the patients; Campylobacter in 9.2%. The prevalence of Campylobacter was significantly lower than in a similar study in 1992-1993. The total percentage of patients in which a pathogen could be found was 39%. This percentage increased to 49% when excluding patients who had gastrointestinal complaints for more than a week before consulting a GP, patients whose samples were in the mail-system for more than two days and patients who had used antibiotics in the week before submitting the sample.

RIVM rapport:Doel van dit onderzoek was om een methode te ontwikkelen voor de detectie van SRSV, met behulp van de reverse transcriptase-polymerase chain reaction (RT-PCR), in riool- en oppervlakte water (concentraten). In eerste instantie werd de RT-PCR geoptimaliseerd met behulp van SRSV positieve faeces, en werden twee RNA opwerkmethoden vergeleken (polyethyleen glycol (PEG)/cetyltri-methylammonium bromide (CTAB) en guanidinium isothiocyanaat (GuSCN)/silica). Rioolwater en 3% beef extract werden kunstmatig besmet met poliovirus serotype 3 voor gebruik als model systeem, omdat poliovirus in tegenstelling tot SRSV wel gekweekt kan worden, en met behulp van de plaque overlay methode gekwantificeerd kan worden. Twee opwerkmethoden voor monsters water zijn met elkaar vergeleken: een methode gebaseerd op twee-fasen scheiding en een precipitatiemethode. De virus opbrengst (poliovirus) werd zowel met celkweek als met RT-PCR bepaald. Met de twee-fasen scheidingsmethode varieerde de opbrengst tussen 4,8-17,4% wanneer er kunstmatig besmet werd met 10 exp.3 TCID50 ('50% tissue culture infective dose') en tussen 0,7-9,1% wanneer er kunstmatig besmet werd met 10 exp. 5 TCID50. Met de precipitatie methode was de opbrengst ongeveer 0,5%. Gebaseerd op semi-kwantitatieve RT-PCR werden bij SRSV besmette monsters overeenkomstige opbrengsten gevonden. Gebaseerd op deze vergelijking werd de twee-fasen scheidingsmethode geselecteerd voor verdere evaluatie en voor gebruik in veld onderzoek., This study was done to develop and evaluate a method for the detection of Small Round Structured Viruses (SRSV) in sewage and water samples by reverse transcriptase-polymerase chain reaction (RT-PCR). The RT-PCR was first optimized with SRSV positive stool specimens comparing two RNA isolation methods (polyethylene glycol (PEG)/ cetyltrimethylammonium bromide (CTAB) and guanidinium isothiocyanate (GuSCN)/silica). Sewage and 3% beef extract seeded with poliovirus serotype 3 were used as a model system because poliovirus can easily be quantified by plaque assay, unlike SRSV which cannot be cultured. Two methods of water sample concentration and purification were compared, one based on two-phase separation and one based on precipitation. Virus (polio virus) was recovered by cell culture isolation and by RT-PCR. With the two-phase separation method the recovery varied between 4.8-17.4% when samples were seeded with 10 exp. 3 TCID50 ('50% tissue culture infective dose') polio serotype 3 and between 0.7-9.1% when samples were seeded with 10 exp. 5 TCID50 polio serotype 3. With the precipitation method the recovery was approximately 0.5%. Based on semiquantitative RT-PCR, similar recoveries were found for SRSV specimens. Based on this comparison, the two-phase separation method was selected for further evaluation and for use in field studies.

RIVM rapport:Small round-structured viruses (SRSV), ook wel Norwalk-achtige virussen genoemd, zijn belangrijke verwekkers van explosies van gastroenteritis. De detectie van deze groep genetisch uiterst variabele virussen is door de recente ontwikkeling van een generische RT-PCR test sterk vereenvoudigd. Om de incidentie van SRSV bij explosies van gastroenteritis te bepalen, werden in 1996 alle bij de GGD-en gemelde explosies onderzocht volgens een standaardprotocol. Door 28 van de 60 GGD-en werden in totaal 69 explosies gemeld. In 60 van deze explosies (87%), kon met behulp van een RT-PCR SRSV worden aangetoond. Van de 69 gemelde explosies vonden de meeste (78%) in de eerste 3 maanden van 1996 plaats. De meerderheid (59%) van de explosies vond plaats in verpleeg- en verzorgingstehuizen en 25% in ziekenhuizen. Uit sequentie-analyse van de PCR producten bleek, dat stammen van alle explosies in de periode van januari tot november sterk geclusterd waren. Het betrof hier een genogroep II SRSV-type (Grimsby), een type SRSV dat ook al in 1995 in Nederland als predominant type was waargenomen. Vanaf november was een duidelijke shift naar de circulatie van een genogroup I SRSV-type (Venlo) waarneembaar. Samenvattend zijn SRSV de meest frequent voorkomende pathogenen geassocieerd met explosies van gastroenteritis die in 1996 werden gemeld aan de GGD-en in Nederland. De moleculaire analyse laat zien dat SRSV epidemisch verspreiden., Small round-structured viruses (SRSV) are a group of RNA viruses that can cause gastroenteritis in persons of all ages. To determine the incidence of SRSV-associated gastroenteritis in the Netherlands and to study the genetic variability of outbreak strains, all outbreaks that were reported to the epidemiologists of the regional health services in 1996 were investigated using a standardised protocol. In 60 (87%) of the 69 reported outbreaks SRSV could be detected, showing the etiologic significance of SRSV in outbreaks of gastroenteritis in the Netherlands. Of these outbreaks, 84% occurred in semi-closed communities like nursing homes (59%) and hospital wards (25%). Sequence analysis of the outbreak strains revealed that the majority of the strains from January to November 1996 form a tight cluster within genogroup II SRSV. In November 1996, a shift towards genogroup I SRSV occurred, suggesting a change to a new predominant strain.

RIVM rapport:"Small-round-structured viruses" (SRSV) kunnen explosies van gastro-enteritis veroorzaken. Om te onderzoeken in welke mate dit ook in Nederland het geval is, werden alle explosies van gastro-enteritis waarbij diagnostische ondersteuning werd gevraagd van het laboratorium voor Virologie (RIVM) gedurende twee jaar onderzocht op aanwezigheid van SRSV met behulp van een nieuw ontwikkelde test op basis van RT-PCR. Daarnaast werden de gevonden SRSV stammen met behulp van immuno-electronenmicroscopie en sequentie-analyse onderzocht om de antigene en genetische variabiliteit in kaart te brengen. Om dit te kunnen doen werd een generische RT-PCR ontwikkeld waarmee 85% van de SRSV uit de tot nu toe bekende antigene groepen kon worden aangetoond. SRSV werden met electronenmicroscopie en met deze RT-PCR aangetoond in 91% van de gemelde explosies (n=22). Sequentie-analyse van de PCR producten liet zien dat de explosie stammen sterk geclusterd waren. Het merendeel van de SRSV stammen in 1994 is nauw verwant met de twee recent beschreven antigene typen SRSV Toronto virus en Mexico virus. In 1995 vond er een shift plaats naar circulatie van een ander antigeen type (Grimsby), dat genetisch sterk verschilt van de 1994 stammen (27% nt sequentie divergentie). Een vergelijkbare indeling werd gemaakt op basis van antigene typering van de stammen met behulp van immuno-EM. De waargenomen clustering is een sterke aanwijzing voor epidemische verspreiding van SRSV door Nederland., To study the role of 'Small-round-structured viruses' (SRSV) in outbreaks of gastroenteritis in the Netherlands and to evaluate the genetic and antigenic relationships between strains, all outbreaks of gastroenteritis that were reported to RIVM in 1994 and 1995 (n=22) were investigated by EM, single round RT-PCR, and automated sequencing. To enable this, a generic SRSV-specific primer pair was developed which could detect 85% of all known circulating antigenic groups. SRSV could be detected by EM in 86% and by RT-PCR in 91% of the reported outbreaks of gastroenteritis. Partial sequence analysis of the polymerase region of these viruses revealed that there was an apparent clustering of outbreak strains. The majority of the 1994 strains form a tight cluster and are similar to the recently described Toronto virus and Mexico virus. In 1995 there was a shift towards the circulation of a distinct SRSV type, Grimsby, which was quite distinct (27% nt sequence divergence) from the 1994 strains. The molecular typing of the 1994 and 1995 strains was concordant with antigenic typing by SPIEM. These tight clusters of different types of SRSV strongly suggest epidemic spread of SRSV in the Netherlands.

RIVM rapport:In the Netherlands the infection occurs predominantly during the first four years of live and the seasonal activity is highest during early spring. The diagnosis is made more frequently in boys than in girls (56% vs 44%). Most virological laboratories in the Netherlands use latex agglutination (LA) tests for the diagnosis of rotavirus. A total of 205 human faecal specimens were examined for the presence of rotavirus by four different detection methods: latex agglutination (LA) test, a "home-made" enzyme immuno-assay (EIA), polyacrylamide gel electrophoresis (PAGE) and agarose gel electrophoresis (AGE). Identical results in all four tests were found in 188 (92%) of the stool specimens. Using the results of a newly defined golden standard: TRUE, we found the specificities of the LA, EIA, PAGE and AGE to be 97.9, 98.6, 100 and 100%, respectively. The sensitivities of these four methods were 98.4, 98.4, 88.7 and 88.7% respectively. Early diagnosis of rotavirus infection is essential for effective patient management and infection control. LA and AGE are both rapid screening tests for the diagnosis of rotavirus infection. AGE is also an inexpensive test with an added advantage that this method can detect non-group A rotaviruses. During our survey, we could not identify non-group A rotaviruses. The epidemiology of rotavirus gastroenteritis in the Netherlands was investigated by serotyping. We compared two different methods for serotyping 84 faecal rotavirusstrains from patients with gastroenteritis: serotyping by an enzyme immunoassay with serotype-specific monoclonal antibodies and gen amplification with type-specific oligonucleotide primers. With the PCR typing method we could type 96%, and with the EIA MAb 82% of the 84 faecal strains. 100% agreement of the result was observed with all the samples that were typed by both assays. Serotype 1 rotavirus was predominant in the Netherlands in 1990 with a prevalence of 77%. The prevalence of serotype 2,3 and 4 was 3,3 and 17%