Emergence of Norovirus GII.4 variants in acute gastroenteritis outbreaks in South Korea between 2006 and 2013

BackgroundNew emerging strains of noroviruses (NoVs) often increase acute gastroenteritis (AGE) outbreaks worldwide.ObjectiveWe analyzed the epidemiological features and genotypic patterns of NoVs in AGE outbreaks.Study designTo elucidate the public health impact of NoVs during AGE outbreaks in South Korea, a molecular and epidemiological investigation was performed with 318 AGE outbreaks reported from the Gyeonggi province of South Korea during the period from 2006 to 2013.ResultsNoVs were associated with 102 (32.1%) of the AGE outbreaks. Epidemiological data revealed that the majority of NoV outbreaks were in the student group (47.1%), and the majority of AGE patients were identified in schools (68.8%). NoV genogroup (G) II strains were associated with 94 (92.2%) of the NoV outbreaks, and GII.4 strains were predominantly associated with 57.6% (n = 49) of NoV GII outbreaks. Four GII.4 variants (2006b, 2007, 2009 and 2012 variants) emerged and showed different contributions to NoV outbreak activity. The 2006b variant was predominantly associated with NoV outbreaks during the early years of the study period, and was subsequently displaced by the New Orleans 2009 variant, and most recently by the Sydney 2012 variant. In addition, the GII.2, GII.14, and GII.17 strains have recently been often associated with NoV AGE outbreaks.ConclusionsThe emergence of new NoV GII.4 variants significantly affected the NoV outbreak activity in South Korea during the period from 2006 to 2013. The surveillance for new emerging strains affecting NoV outbreak activity should be intensified to develop an adequate policy to prevent further NoV outbreaks.     

Emergence of a new norovirus GII.6 variant in Japan, 2008-2009

Norovirus (NoV) is recognized as one of the most common causative agents of diarrhea disease in young children. A total of 187 fecal specimens collected from non-hospitalized children with acute gastroenteritis in Shizuoka, Japan during July 2008 to June 2009 were investigated for the presence of diarrhea viruses by a multiplex RT-PCR. Diarrhea viruses were overall detected in 158 of 187 (84.5%). Of the viruses detected, NoV was the most prevalent (55.6%). Most of the NoV sequences belonged to GII.4 (53.8%). NoV GII.6 emerged as the second most common strain (40.4%). The full-length capsid sequences of five representative Shizuoka GII.6 strains were compared with all 12 GII.6 strains available in GenBank database between 1990 and 2009. At least three distinct GII.6 subclusters (a-c) appeared in different parts of the world. Shizuoka GII.6 strains formed their own subcluster c, distinct from other complete GII.6 reference sequences. The Shizuoka strains had significant amino acid divergence, particularly in the P2 domain up to 10.9-17.5% and contained eight unique mutations in the P domains, compared with subcluster a and b viruses. The homology model showed that the eight mutations were predicted to be located at the surface-exposed P1 and P2 domains. The data suggest the emergence of a new NoV GII.6 variant in Shizuoka, with a high level of genetic variation.     

Norovirus GII.4 variant 2006b caused epidemics of acute gastroenteritis in Australia during 2007 and 2008

BackgroundOver the last decade, four epidemics of norovirus-associated gastroenteritis have been reported in Australia. These epidemics were characterized by numerous outbreaks in institutional settings such as hospitals and nursing homes, as well as increases in requests for NoV testing in diagnostic centers. During 2007 and 2008, widespread outbreaks of acute gastroenteritis were once again seen across Australia, peaking during the winter months.ObjectivesThe primary objective of this study was to characterize two winter epidemics of NoV-associated gastroenteritis in 2007 and 2008 in Australia. Following this, we aimed to determine if these epidemics were caused by a new GII.4 variant or a previously circulating NoV strain.Study designNoV-positive fecal samples (n = 219) were collected over a 2-year period, December 2006 to December 2008, from cases of acute gastroenteritis in Australia. NoV RNA was amplified from these samples using a nested RT-PCR approach targeting the 5′ end of the capsid gene, termed region C. Further, characterization was performed by sequence analysis of the RdRp and capsid genes and recombination was identified using SimPlot.ResultsFrom 2004 to 2008, peaks in the numbers of NoV-positive EIA tests from the Prince of Wales Hospital Laboratory correlated with the overall number of gastroenteritis outbreaks reported to NSW Health, thereby supporting recent studies showing that NoV is the major cause of outbreak gastroenteritis. The predominant NoV GII variant identified during the 2007–2008 period was the GII.4 pandemic variant, 2006b (71.51%, 128/179), which replaced the 2006a variant identified in the previous Australian epidemic of 2006. Four novel GII variants were also identified including the three GII.4 variants: NoV 2008, NoV Osaka 2007 and NoV Cairo 2007, and one novel recombinant NoV designated GII.e/GII.12.ConclusionThe increase in acute gastroenteritis outbreaks in 2007 and 2008 were associated with the spread of the NoV GII.4 variant 2006b.     

Antibody Responses to Norovirus Genogroup GI.1 and GII.4 Proteases in Volunteers Administered Norwalk Virus

An assay was developed to detect antibodies against two norovirus proteases among participants in a Norwalk virus (GI.1) challenge study. Prechallenge seroprevalence was lower against the protease from the homologous GI.1 virus than against protease from a heterologous GII.4 strain. Seroresponses were detected for 14 of 19 (74%) infected persons.     

Emergence of the GII4/2006b variant and recombinant noroviruses in China

Noroviruses are an important cause of acute gastroenteritis. Increasing data showed that the GII-4 strains are predominant worldwide and new GII-4 variants emerge every 1-2 years causing major epidemics. Surveillance of gastroenteritis in hospitalized children under 5 years of age in China is described. Among 1,110 specimens, 114 (10.3%) were positive for noroviruses, which was higher than adenoviruses (7.6%), astroviruses (3.5%), and sapoviruses (0.9%) and only lower than group A rotaviruses (40.6%). Thirty-eight of the 114 positive norovirus cases were co-infected with other enteric viruses. Five norovirus genotypes (GI-2, GI-4, GII-3, GII-4, and GII-14) were detected, with GII-4/2006b the most predominant type (64.9%). The reported recombinant of GII-3 capsid and GII-4 polymerase described previously was also detected frequently and a recombinant of GII-14 capsid and GII-6 polymerase was found for the first time. This study suggests that continual surveillance focusing on strain variation and dynamic change is important for understanding the epidemiology and development of a strategy for disease control and prevention.     

Identification and characterization of a native epitope common to norovirus strains GII/4, GII/7 and GII/8

Norovirus is an important cause of acute non-bacterial gastroenteritis in humans. The norovirus genus is comprised of at least five genogroups based on sequence differences. The norovirus genogroup II (GII/4) strain is recognized as the predominant genotype worldwide. We expressed a 60 kDa full-length recombinant capsid protein of norovirus GII/4 in Escherichia coli and generated three monoclonal antibodies (MAbs) against it. Western blotting indicated that all three MAbs had reactivity against the recombinant capsid protein and a 58 kDa native capsid protein of norovirus obtained from stool samples. MAb-capture ELISA showed that MAb detected segmental strains within GII antigens in clinical material. To identify the existent range of this epitope, epitope analyses were processed by expressing 12 amino acids of the GST-fusion peptides. The epitope analyses revealed that the MAb N2C3 recognized a continuous native epitope ⁵⁵WIRNNF⁶⁰ in the shell domain, which not only belongs to strain GII/4, but also to strains GII/7 and GII/8. This is a new native epitope to be reported for norovirus GII/4.     

Genotypic and Epidemiologic Trends of Norovirus Outbreaks in the United States, 2009 to 2013

Noroviruses are the leading cause of epidemic acute gastroenteritis in the United States. From September 2009 through August 2013, 3,960 norovirus outbreaks were reported to CaliciNet. Of the 2,895 outbreaks with a known transmission route, person-to-person and food-borne transmissions were reported for 2,425 (83.7%) and 465 (16.1%) of the outbreaks, respectively. A total of 2,475 outbreaks (62.5%) occurred in long-term care facilities (LTCF), 389 (9.8%) in restaurants, and 227 (5.7%) in schools. A total of 435 outbreaks (11%) were typed as genogroup I (GI) and 3,525 (89%) as GII noroviruses. GII.4 viruses caused 2,853 (72%) of all outbreaks, of which 94% typed as either GII.4 New Orleans or GII.4 Sydney. In addition, three non-GII.4 viruses, i.e., GII.12, GII.1, and GI.6, caused 528 (13%) of all outbreaks. Several non-GII.4 genotypes (GI.3, GI.6, GI.7, GII.3, GII.6, and GII.12) were significantly more associated with food-borne transmission (odds ratio, 1.9 to 7.1; P < 0.05). Patients in LTCF and people ≥65 years of age were at higher risk for GII.4 infections than those in other settings and with other genotypes (P < 0.05). Phylogeographic analysis identified three major dispersions from two geographic locations that were responsible for the GI.6 outbreaks from 2011 to 2013. In conclusion, our data demonstrate the cyclic emergence of new (non-GII.4) norovirus strains, and several genotypes are more often associated with food-borne outbreaks. These surveillance data can be used to improve viral food-borne surveillance and to help guide studies to develop and evaluate targeted prevention methods such as norovirus vaccines, antivirals, and environmental decontamination methods.     

Emergence of norovirus GII-4/2008 variant and recombinant strains in Seoul, Korea

Recently, the emergence of a new NoV GII-4 variant strain every 2 or 3 years has been reported. One hundred seventeen NoV GII strains were detected by RT-PCR in children with AGE between August 2008 and February 2010. In phylogenetic analyses, GII-4 and GII-3 were the most frequently detected strains. The detection rate of the 2008 variant was similar to that of the 2006b variant in the winter seasons of 2009 and 2010. This study shows a changing pattern of a predominant GII-4/2006b variant to the 2008 variant, as well as a novel NoV recombinant strain, GII-6/GII-14, in Korea.     

Genomics-Based Molecular Epidemiology of Campylobacter jejuni Isolates from Feedlot Cattle and from People in Alberta, Canada

Feedlot cattle in Alberta, Canada, have been identified as reservoirs for Campylobacter jejuni, an important human pathogen. Oligonucleotide DNA microarrays were used as a platform to compare C. jejuni isolates from feedlot cattle and human clinical cases from Alberta. Comparative genomic hybridization (CGH) analysis was performed on 87 isolates (46 bovine, 41 human) obtained within the same geographical regions and time frame. Thirteen CGH clusters were obtained based on overall comparative genomic profile similarity. Nine CGH clusters contained human and cattle isolates, three contained only human isolates, and one contained only cattle isolates. The study isolates clustered regardless of temporal or geographical frameworks. In addition, array genes (n = 1,399) were investigated on a gene-by-gene basis to see if any were unequally distributed between human and cattle sources or between clusters dominated by either human or cattle isolates (“human enriched” versus “cattle enriched”). Using Fisher's exact test with the Westfall and Young correction for these comparisons, a small number of differentially distributed genes were identified. Our findings suggest that feedlot cattle and human C. jejuni strains are very similar and may be endemic within Alberta. Further, the common distribution of human clinical and bovine C. jejuni isolates within the same genetically based clusters suggests that dynamic and important transmission routes between cattle and human populations may exist.     

Measurement of the virolysis of human GII.4 norovirus in response to disinfectants and sanitisers

The aim of this study was to develop a method for investigating the stability of the human NoV capsid in response to disinfectants and sanitisers (virucides) as an indirect method for determining virus infectivity. Capsid destruction or "virolysis" was measured using the reverse transcribed quantitative PCR (RT-QPCR) reaction in conjunction with RNase treatment (in order to destroy any exposed RNA). Two commercially available alcohol based handwashes, alcohols (75% (v/v) ethanol or isopropanol), quaternary ammonium compounds (0.14% BAC or 0.07% DIDAC), and chlorine dioxide (200 ppm) were all ineffective at promoting virolysis of human norovirus present in dilute clinical samples at the concentrations tested. GII.4 NoVs were sensitive to a combination of heat and alkali. These data show that NoVs present in dilute stool samples are resistant to virolysis using virucides that are used commonly.     

Norovirus strains belonging to the GII.4 genotype dominate as a cause of nosocomial outbreaks of viral gastroenteritis in Sweden 1997--2005. Arrival of new variants is associated with large nation-wide epidemics.

BACKGROUND: In recent years an increase of the incidence of nosocomial outbreaks caused by noroviruses has been observed throughout Sweden, with high peaks noted in the winter seasons 2002/2003 and 2004/2005, respectively. OBJECTIVES: To phylogenetically characterize norovirus strains causing nosocomial outbreaks from 1997 to 2005 and estimate the impact of norovirus-like disease on the Swedish health care system during the peak season 2002/2003 when a new variant of norovirus occurred. STUDY DESIGN: Stool samples from 115 randomly selected nosocomial outbreaks occurring during 1997--2005 throughout Sweden were studied by RT-PCR and sequencing. In addition, to investigate the impact on the health-care system, a questionnaire was distributed to infection control units (n=90) serving all Swedish hospitals, nursing homes and other health-care institutions during the largest epidemic of nosocomial outbreaks. RESULTS: Sequencing of 279 nucleotides of the norovirus RNA polymerase gene in stools containing norovirus RNA showed that strains belonging to the GII.4 genotype dominated. Each of the two large epidemics was due to a new variant within this cluster. The questionnaire revealed that 30,000-35,000 episodes of nosocomial norovirus-like infections occurred in 80 of 82 major Swedish hospitals affected in 2002/2003. CONCLUSION: New norovirus variants within the cluster GGII.4 may have a major impact on the health-care system.