NoV Infection Research Articles

Detection of norovirus infections in Denmark, 2011-2018.

Norovirus (NoV) infections occur very frequently yet are rarely diagnosed. In Denmark, NoV infections are not under surveillance. We aimed to collect and describe existing laboratory-based NoV data. National NoV laboratory data were collected for 2011-2018, including information on patient identification number, age and sex, requesting physician, analysis date and result. We defined positive patient-episodes by using a 30-day time window and performed descriptive and time series analysis. Diagnostic methods used were assessed through a survey. We identified 15 809 patient-episodes (11%) out of 142 648 tested patients with an increasing trend, 9366 in 2011 vs. 32 260 in 2018. This corresponded with a gradual introduction of polymerase chain reaction analysis in laboratories. The highest positivity rate was in patients aged <5 years (15%) or >85 years (17%). There was a large difference in test performance over five Danish geographical regions and a marked seasonal variation with peaks from December to February. This is the first analysis of national NoV laboratory data in Denmark. A future laboratory-based surveillance system may benefit public health measures by describing trend, burden and severity of seasons and possibly pinpoint hospital outbreaks.

Norovirus contamination of sea urchins (Paracentrotus lividus): Potential food risk for consumers

Sea urchin gonads are today considered a gourmet food but despite eaten raw, not much attention has been given to microbiological quality. This study evaluated the microbial (bacterial and viral) contamination and adequacy to current European regulations of Paracentrotus lividus sea urchins produced in Portugal.Four batches of 10 sea urchins were collected (September 2016 to May 2017) from the sea floor of a natural urchin growing area located in the north of Portugal. Sea urchin gonad batches were analysed for E. coli and Salmonella spp. as governed by the Commission Regulation (EC) No 2073/2005, modified by regulation (EC) No 2015/2285, on microbiological criteria for foodstuffs. Hepatitis A virus, norovirus GI and norovirus GII were also searched for following ISO 15216-1:2017.The four batches were all within the sanitary limits imposed by legislation for E. coli and Salmonella spp. Two batches were found positive for norovirus (one positive for norovirus GI, the other for both norovirus GI and GII), presenting viral concentrations that ranged from 8.7 × 103 and 3.2 × 104 genome copies/g. Sequencing and phylogenetic analysis showed that the obtained sequence clustered with norovirus GI.2.This study is the first evaluating the presence of human pathogenic viruses in live echinoderms and the first reporting NoV contamination of bacteriologically safe sea urchin gonads. NoV infection risk related to consumption of raw sea urchin gonads is in urgent need for evaluation.

High prevalence of norovirus and rotavirus co-infection in children with acute gastroenteritis hospitalised in Brazzaville, Republic of Congo.

To evaluate the clinical severity of diarrhoea associated to viral co-infection in children with acute gastroenteritis. About 461 children under five years hospitalised with acute diarrhoea (266 males and 187 females) were enrolled in the study. Using stool samples, rotavirus and adenovirus infections were investigated by ELISA, and norovirus infections by nested duplex RT-PCR. We assessed social, demographic, clinical and behavioural conditions that might influence the occurrence of rotavirus, adenovirus and norovirus infections. Mono-viral infection was detected in 49% and mixed viral infection in 12% of patients. The prevalence of mixed infection was neither dependent on age nor sex. Three samples were infected with all three viruses. A significant association was found between fever (axillary temperature>37.5°C) and rotavirus-norovirus dual infection (aOR (CI 95%) = 2.1 (1.14-3.84), P=0.016; aOR (CI 95%) = 0.37 (0.19-0.73), P=0.004). Mixed infection was the most common during the dry season from June to October (71.4% versus 54.7%, P=0.023). Co-infection with both rotavirus and norovirus is common in under-five hospitalised children but does not contribute to the severity of the disease.

78. Oral Norovirus Vaccination in Humans Induces Plasmablast B-Cell Expansion and Follicular T-Cell Activation Comparable to Natural Infection

BackgroundNorovirus (NoV) is a common cause of acute gastroenteritis, but no vaccines are currently licensed. Vaxart is developing an oral tableted NoV vaccine that induces both systemic and mucosal immune responses.MethodsTwo separate clinical studies were conducted to evaluate the safety and immunogenicity of an oral NoV vaccine and NoV infection. The first study investigated an oral tablet vaccine based on a recombinant adenovirus vector expressing NoV VP1 (rAd-VP1). In the second study, a controlled NoV infection (Norwalk virus) was performed using a strain isolated and purified from an infected subject. Serum and PBMCs were collected pre- and post-immunization/infection. Serum immune responses were assessed using IgG/IgA ELISAs and blocking titer (BT50) assays. Cellular immune responses were evaluated using antibody-secreting cell (ASC) assays to quantitate norovirus-specific B cells. Flow cytometry was used to analyze the phenotype of circulating B and T cells.ResultsThe rAd-VP1 vaccine was well tolerated whereas most subjects (56%) in the controlled infection study had significant gastroenteritis 2–4 days post-inoculation. Subjects in cohorts vaccinated 28 days apart with 1 × 1010 or 1 × 1011 IUs showed the highest rises in serum IgG and IgA titers compared with those immunized 2 or 7 days apart with a 1 × 1010 IU vaccine dose. Subjects in the 1 × 1011 IU vaccine dose cohort had a 6-fold rise in serum IgA and 4-fold rise in BT50 titers, with mean IgA and IgG ASC values of 698 and 389 counts, respectively. In comparison, NoV-challenged subjects showed an average of 2,072 IgA and 886 IgG ASC counts. Remarkably, flow cytometry analysis revealed that activated B- and T-cell responses were similar post-vaccination and post-infection, with significant expansion of T follicular cells, plasmablasts, mucosal homing B cells, and preferential activation of IgA B cells.ConclusionThe phenotype of activated B and T cells induced post-immunization was similar to that induced post-infection, suggesting that an oral vaccine can induce comparable adaptive immune responses without the substantial adverse clinical events that occur from natural infection. Future work in dose ranging will aide in the development of a safe and efficacious oral NoV vaccine.Disclosures All Authors: No reported Disclosures.

Molecular epidemiology and clinical characteristics of norovirus gastroenteritis with seizures in children in Taiwan, 2006-2015.

This study examined the characteristics of norovirus (NoV) gastroenteritis associated with convulsions in children and its molecular epidemiology. From July 2006 through December 2015, NoV infection was confirmed by the genome detection using reverse transcriptase polymerase chain reaction. Viral genotyping with strain validation was achieved using sequence analyses with Basic Local Alignment Search Tool genome identification. The patients’ clinical features were assessed retrospectively, focusing on convulsive disorders. The diagnosis of encephalitis followed the International Encephalitis Consortium. Seizures occurred in 52 (20.9%) of 249 NoV infections. GII.4 Den_Haag_2006b (n = 22, 42.3%) and GII.4 Sydney 2012 (n = 10, 19.2%) were major variants correlated with convulsions. Patient with convulsions tend to have GII.4 genotype infection (P < .001), short vomiting (≤2 days) (P < .001), and no fever (P = .002). Compared to GII.4 Den_Haag_2006b, the GII.4 Sydney 2012-associated convulsions had similar manifestations except without significant winter preponderance (P = .049). The NoV infection with convulsions had less febrile course, specific genotype (GII.4) infections, and with shorter symptom of vomiting. Continuous surveillance is important for uncommon disease associated with emerging NoV strain infections. The prevention of NoV diseases requires the development of vaccines targeting highly virulent variants.

Genetic diversity and epidemiology of Genogroup II noroviruses in children with acute sporadic gastroenteritis in Shanghai, China, 2012\u20132017

BackgroundNoroviruses (NoVs) are considered an important cause of acute gastroenteritis (AGE) across all age groups, especially in children under 5 years of age. We investigated the epidemiology of noroviruses in outpatient children from the Children’s Hospital of Fudan University in Shanghai, China.MethodsStool specimens were collected between January 2012 and December 2017 from 1433 children under 5 years of age with acute gastroenteritis. All samples were analysed by conventional reverse transcription-polymerase chain reaction (RT-PCR) for genogroup II NoVs amplifying both the RNA-dependent RNA polymerase (RdRp) and partial capsid genes. The Norovirus Genotyping Tool v.2.0 (https://www.rivm.nl/mpf/typingtool/norovirus/) was used for genotyping the strains, and phylogenetic analyses were conducted by MEGA 6.0.ResultsFrom 2012 to 2017, GII NoVs were detected in 15.4% (220/1433) of the samples, with the highest detection rate in children aged 7–12 months (19.2%, 143/746). The seasons with the highest prevalence of GII NoVs infection were autumn and winter. Based on genetic analysis of RdRp, GII.Pe (74.5%%, 137/184) was the most predominant RdRp genotype from 2013 to 2017, while GII.P4 played a dominant role in 2012 (55.6%, 21/36). Among the capsid genotypes, the most prevalent NoV genotype from 2012 to 2017 was GII.4 (74.1%, 163/220). On the basis of genetic analysis of RdRp and capsid sequences, the strains were clustered into − 19 RdRp/capsid genotypes, and 12 of them were discordant, such as GII.Pe/GII.4-Sydney_2012, GII.P12/GII.3, GII.P7/GII.6, GII.Pe/GII.3, and GII.P16/GII.2. Starting with 2013, GII.Pe/GII.4-Sydney_2012 had completely replaced the pandemic GII.P4-2006b/GII.4-2006b subtype and was detected in children across all age groups.ConclusionsThe present study shows high detection rates and the genetic diversity of circulating NoV GII genotypes in paediatric AGE samples from Shanghai. The findings emphasize the importance of continuous molecular surveillance of emerging NoV strains.

Norovirus shedding among symptomatic and asymptomatic employees in outbreak settings in Shanghai, China

BackgroundNorovirus (NoV) is recognized as a leading cause of acute gastroenteritis (AGE) outbreaks in settings globally. Studies have shown that employees played an important role in the transmission mode during some NoV outbreaks. This study aimed to investigate the prevalence of NoV infection and duration of NoV shedding among employees during NoV outbreaks, as well as factors affecting shedding duration.MethodsSpecimens and epidemiological data were collected from employees who were suspected of being involved in the transmission or with AGE symptoms during NoV outbreaks in Xuhui District, Shanghai, from 2015 to 2017. Specimens were detected using real-time RT-PCR to determine whether or not employees had become infected with NoV. Specimens were collected every 3–7 days from NoV-infected employees until specimens became negative for NoV.ResultsA total of 421 employees were sampled from 49 NoV outbreaks, and nearly 90% of them (377/421) were asymptomatic. Symptomatic employees showed significantly higher prevalence of NoV infection than asymptomatic ones (70.5% vs. 17.0%, P < 0.01). The average duration of NoV shedding was 6.9 days (95% confidence interval: 6.1–7.7 days) among 88 NoV-infected individuals, and was significantly longer in symptomatic individuals than in asymptomatic ones (9.8 days vs. 5.6 days, P < 0.01). In Cox proportional-hazards model, after adjusting age and gender, symptoms was the only factor associated with duration of NoV shedding.ConclusionsCompared with asymptomatic employees, symptomatic employees had higher prevalence of NoV infection and longer durations of NoV shedding. Since NoV shedding duration among NoV-infected employees tends to be longer than their isolation time during outbreaks, reinforcement of hygiene practices among these employees is especially necessary to reduce the risk of virus secondary transmissions after their return to work.

Molecular epidemiology of norovirus associated with acute gastroenteritis in Taizhou, China: A retrospective study

BackgroundNorovirus (NoV) is recognized as a leading global cause of viral acute gastroenteritis (AGE). To better understand the prevalence and genotypic patterns of NoV infection in Southeast China, we conducted a retrospective study of diarrheal syndrome surveillance of NoV and analyzed the epidemiological characteristics of AGE cases and phylogenetic evolution of NoV strains. Methods1464 AGE patients in two diarrhea surveillance sentinel hospitals were sampled during 2016 and 2017. NoV Positive samples were genotyped by ORF1/ORF2 overlapping regional gene sequencing. Sequences analyses of the NoV genotypes were confirmed by online NoV Genotyping Tool and the phylogenetic analysis was constructed by MEGA 7.0. Results139 (9.49%) of the AGE specimens were NoV positive. The GII strain was the main geno-group in NoV infected patients. At least 12 NoV genotypes and seven recombinant strains were detected. Major NoV genotypic transformations were GII.Pe/GII.4, GII.P17/GII.17 and GII.Pe/GII.17 in 2016 to GII.P16/GII.2, GII.P17/GII.17 and GII.Pe/GII.4 in 2017. Phylogenetic analysis showed that GII.P16/GII.2 recombinant strains clustered with those detected in the USA, Russia and Japan in 2016. ConclusionWe characterized the molecular epidemiology of NoV infection in AGE patients during 2016–2017. The main three NoV GII genotypes circulating in the population of Taizhou were GII.P17/GII.17, GII.Pe/GII.4 and GII.P16/GII.2.The GII.P16/GII.2 genotype has become the predominant strain since first quarter 2017. Monitoring of the NoV genotypic shift is important for the prevention and control of AGE.

GII.4 Norovirus Protease Shows pH-Sensitive Proteolysis with a Unique Arg-His Pairing in the Catalytic Site.

Human noroviruses (NoVs) are the main cause of epidemic and sporadic gastroenteritis. Phylogenetically, noroviruses are divided into seven genogroups, with each divided into multiple genotypes. NoVs belonging to genogroup II and genotype 4 (GII.4) are globally most prevalent. Genetic diversity among the NoVs and the periodic emergence of novel strains present a challenge for the development of vaccines and antivirals to treat NoV infection. NoV protease is essential for viral replication and is an attractive target for the development of antivirals. The available structure of GI.1 protease provided a basis for the design of inhibitors targeting the active site of the protease. These inhibitors, although potent against the GI proteases, poorly inhibit the GII proteases, for which structural information is lacking. To elucidate the structural basis for this difference in the inhibitor efficiency, we determined the crystal structure of a GII.4 protease. The structure revealed significant changes in the S2 substrate-binding pocket, making it noticeably smaller, and in the active site, with the catalytic triad residues showing conformational changes. Furthermore, a conserved arginine is found inserted into the active site, interacting with the catalytic histidine and restricting substrate/inhibitor access to the S2 pocket. This interaction alters the relationships between the catalytic residues and may allow for a pH-dependent regulation of protease activity. The changes we observed in the GII.4 protease structure may explain the reduced potency of the GI-specific inhibitors against the GII protease and therefore must be taken into account when designing broadly cross-reactive antivirals against NoVs.IMPORTANCE Human noroviruses (NoVs) cause sporadic and epidemic gastroenteritis worldwide. They are divided into seven genogroups (GI to GVII), with each genogroup further divided into several genotypes. Human NoVs belonging to genogroup II and genotype 4 (GII.4) are the most prevalent. Currently, there are no vaccines or antiviral drugs available for NoV infection. The protease encoded by NoV is considered a valuable target because of its essential role in replication. NoV protease structures have only been determined for the GI genogroup. We show here that the structure of the GII.4 protease exhibits several significant changes from GI proteases, including a unique pairing of an arginine with the catalytic histidine that makes the proteolytic activity of GII.4 protease pH sensitive. A comparative analysis of NoV protease structures may provide a rational framework for structure-based drug design of broadly cross-reactive inhibitors targeting NoVs.

Seroprevalence for norovirus genogroups GII and GIV in captive non‐human primates

Noroviruses (NoVs) are a major cause of epidemic gastroenteritis in children and adults. Several pieces of evidence suggest that viruses genetically and antigenically closely related to human NoVs might infect animals, raising public health concerns about potential cross-species transmission. The natural susceptibility of non-human primates (NPHs) to human NoV infections has already been reported, but a limited amount of data is currently available. In order to start filling this gap, we screened a total of 86 serum samples of seven different species of NPHs housed at the Zoological Garden (Bioparco) of Rome (Italy), collected between 2001 and 2017, using an enzyme-linked immunosorbent assay (ELISA) based on virus-like particles (VLPs) of human GII.4 and GIV.1 NoVs. Antibodies specific for both genotypes were detected with an overall prevalence of 32.6%. In detail, IgG antibodies against GII.4 NoVs were found in 18 Japanese macaques (29.0%, 18/62), a mandrill (10.0%, 1/10), a white-crowned mangabey (16.6%, 1/6) and in an orangutan (33.3%, 1/3). Twelve macaques (19.3%, 12/62), five mandrills (50.0%, 5/10), two chimpanzees (100%, 2/2) and a white-crowned mangabey (16.6%, 1/6) showed antibodies for GIV.1 NoVs. The findings of this study confirm the natural susceptibility of captive NHPs to GII NoV infections. In addition, IgG antibodies against GIV.1 were detected, suggesting that NHPs are exposed to GIV NoVs or to antigenically related NoV strains.

Emergence of norovirus GII.P16-GII.2 strains in patients with acute gastroenteritis in Huzhou, China, 2016\u20132017

BackgroundIn late 2016, an uncommon recombinant NoV genotype called GII.P16-GII.2 caused a sharp increase in outbreaks of acute gastroenteritis in different countries of Asia and Europe, including China. However, we did not observe a drastic increase in sporadic norovirus cases in the winter of 2016 in Huzhou. Therefore, we investigate the prevalence and genetic diversity of NoVs in the sporadic acute gastroenteritis (AGE) cases from January 2016 to December 2017 in Huzhou City, Zhejiang, China.MethodsFrom January 2016 to December 2017, a total of 1001 specimens collected from patients with AGE were screened for NoV by real-time RT-PCR. Partial sequences of the RNA-dependent RNA polymerase (RdRp) and capsid gene of the positive samples were amplified by RT-PCR and sequenced. Genotypes of NoV were confirmed by online NoV typing tool and phylogenetic analysis. Complete VP1 sequences of GII.P16-GII.2 strains detected in this study were further obtained and subjected into sequence analysis.ResultsIn total, 204 (20.4%) specimens were identified as NoV-positive. GII genogroup accounted for most of the NoV-infected cases (98.0%, 200/204). NoV infection was found in all age groups tested (< 5, 5–15, 16–20, 21–30, 31–40, 41–50, 51–60, and >60 years), with the 5–15 year age group having the highest detection rate (17/49, 34.7%). Higher activity of NoV infection could be seen in winter-spring season. The predominant NoV genotypes have changed from GII.Pe-GII.4 Sydney2012 and GII.P17-GII.17 in 2016 to GII.P16-GII.2, GII.Pe-GII.4 Sydney2012 and GII.P17-GII.17 in 2017. Phylogenetic analyses revealed that 2016–2017 GII.P16-GII.2 strains were most closely related to Japan 2010–2012 cluster in VP1 region and no common mutations were found in the amino acids of the HBGA-binding sites and the predicted epitopes.ConclusionsWe report the emergence of GII.P16-GII.2 strains and characterize the molecular epidemiological patterns NoV infection between January 2016 and December 2017 in Huzhou. The predominant genotypes of NoV during our study period are diverse. VP1 amino acid sequences of 2016–2017 GII.P16-GII.2 strains remain static after one year of circulation.

Quantitative microbial risk assessment to estimate the health risk from exposure to noroviruses in polluted surface water in South Africa.

This study assessed the risks posed by noroviruses (NoVs) in surface water used for drinking, domestic, and recreational purposes in South Africa (SA), using a quantitative microbial risk assessment (QMRA) methodology that took a probabilistic approach coupling an exposure assessment with four dose-response models to account for uncertainty. Water samples from three rivers were found to be contaminated with NoV GI (80-1,900 gc/L) and GII (420-9,760 gc/L) leading to risk estimates that were lower for GI than GII. The volume of water consumed and the probabilities of infection were lower for domestic (2.91 × 10-8 to 5.19 × 10-1) than drinking water exposures (1.04 × 10-5 to 7.24 × 10-1). The annual probabilities of illness varied depending on the type of recreational water exposure with boating (3.91 × 10-6 to 5.43 × 10-1) and swimming (6.20 × 10-6 to 6.42 × 10-1) being slightly greater than playing next to/in the river (5.30 × 10-7 to 5.48 × 10-1). The QMRA was sensitive to the choice of dose-response model. The risk of NoV infection or illness from contaminated surface water is extremely high in SA, especially for lower socioeconomic individuals, but is similar to reported risks from limited international studies.

Burden of acute gastroenteritis caused by norovirus in China: A systematic review

To understand the epidemiology and disease burden of norovirus (NoVs) gastroenteritis in China, a systematic review was conducted. Studies on acute gastroenteritis (AGE) caused by NoVs from mainland China, published before 2017 were searched. All retrieved articles were screened and reviewed by a standardized algorithm. NoVs detection rates as well as strain variations by ages, seasonal variations and geographic locations were analyzed using random-effects model. A total of 225 articles were included in the final analysis. Similar detection rates at 21.0% and 19.8% were obtained from the North and the South, respectively. NoVs infection occurred year round, with a peak between October and January in the North and between August and November in the South. High detection rates (∼29%) of NoVs were found in adults and the elderly and in children aged 6-35 months (∼22%). The predominant strains were GII.4 (70.4%), followed by GII.3 (13.5%). NoVs cause significant disease burden in China which warrants development of vaccines against NoVs, particularly for children and the elderly who are vulnerable to gastroenteritis diseases. To achieve a broad protection, continual monitoring NoV epidemics and strain variations for selection of proper vaccine strains is critical.

Severity and outcome of the norovirus infection in children after intestinal transplantation.

In immunocompromised patients, the NoV infection is prolonged and severe. We retrospectively studied the severity of the NoV infection in children after an ITx, the treatment, and the long-term evolution. Norovirus PCR in stools was positive for 19 children in 21 separate episodes. The infection was symptomatic in 18 cases. At diagnosis, the median weight loss was 5% (0-11) and the creatinine clearance was 75mL/min/1.73m2 (19-142). On 14 digestive biopsies, the pathological findings were non-specific with a constant mononuclear infiltration, showing signs of rejection in one case. Fifteen children in 17 cases were hospitalized for a median duration of 41days (0-119) with IV infusions for 33days (0-120). The viral shedding lasted 78days (20-360). Nine children with severe or prolonged diarrhea received intravenous IGs and four of them additional NTZ. On follow-up, five other children developed a rejection 12months (1-33) after NoV infection. Four uncontrolled rejections led to graft removal. Children mostly needed hospital admission and IV rehydration, but the symptoms upon presentation were moderate. Symptoms and shedding durations are prolonged as expected. The treatment efficacy cannot be assessed. The rejection induction by the NoV cannot be excluded.

Noroviruses in livestock, pets and public health impact.

Abstract Noroviruses (NoVs) are a leading cause of acute gastroenteritis (diarrhoea and vomiting) worldwide. The virus was reported from humans and later was identified in different symptomatic and/or asymptomatic animal species, such as bovine, ovine, swine, canine and feline. In animals NoV infection is supposedly associated with enteritis; however, the pathogenic role of NoV infection and its impact in animal health are currently uncertain. NoVs have a positive sense, single-stranded RNA genome of diverse molecular feature. Currently, NoVs are classified into six genogroups (GI-GVI), with the proposed seventh (GVII) and at least 31 genotypes. The GI, GV and GVI are species-specific genogroups, while the GII, GIII and GIV share different host species, including humans. The close genetic relationship among different NoV strains detected from both humans and animals raised the possibility of this virus has zoonotic potential. This review aimed to address the NoV classification, morphological and molecular features, epidemiology, pathogenesis and pathology, diagnosis, treatment and management. A broad approach is given on the importance of NoVs as a cause of disease in livestock and pets and on studies into the potential for zoonotic transmission and public health.

Clinical and molecular analyses of norovirus-associated sporadic acute gastroenteritis: the emergence of GII.17 over GII.4, Huzhou, China, 2015.

BackgroundNoroviruses (NoVs) are the most common cause of non-bacterial acute gastroenteritis (AGE) in all age groups worldwide. The NoVs circulating in Huzhou over the past 7 years were predominantly GII.4 genotypes. In the winter of 2014–2015, a novel variant of NoV GII.17 emerged and became predominant. We report the epidemiological patterns and genetic characteristics of NoV after the appearance of GII.17 in Huzhou City, Zhejiang, China.MethodsBetween January and December 2015, 746 stool specimens collected from patients with acute gastroenteritis were screened for NoV. Real-time RT-PCR (qPCR) was performed for NoV detection. RT-PCR was used for genomic amplification and sequencing. Genogroups and genotypes were assigned using an online NoV typing tool (http://www.rivm.nl/mpf/norovirus/typingtool). Phylogenetic analyses were conducted using MEGA (ver. 6.06).ResultsIn total, 196 (26.3%) specimens were identified as NoV-positive. NoV infection was found in all age groups tested (≤5, 6–15, 16–40, 41–60, and ≥60 years), with the 16–40-year age group having the highest detection rate (117/196, 59.7%). Of the 196 NoV-positive specimens, 191 (97.5%) viruses belonged to GII, and 4 (2.0%) to GI; one sample showed GI and GII co-infection. Overall, 117 (59.7%) viruses were sequenced, and new GII.P17/GII.17 variants were the dominant genotype, accounting for 75.2%, followed by GII.Pe/GII.4 Sydney 2012 strains (11.11%). AGE patients infected with the GII.P17/GII.17 genotypes almost all had abdominal pain and watery stools.ConclusionsWe report the epidemiological patterns and genetic characteristics of the emergence GII.17 over the GII.4 in Huzhou between January and December 2015. After the emergence of GII.17 in October 2014, it steadily replaced the previously circulating GII.4 Sydney 2012 strain, and continued to be dominant in 2015.Electronic supplementary materialThe online version of this article (doi:10.1186/s12879-016-2033-x) contains supplementary material, which is available to authorized users.

Effects of disinfectants against norovirus virus-like particles predict norovirus inactivation.

Human noroviruses (NoVs) are a major cause of epidemic and sporadic acute gastroenteritis worldwide. Public and personal hygiene is one of the most important countermeasures for preventing spread of NoV infection. However, no a practicable cell culture system for NoV had been developed, initial tests of the virucidal effectiveness of anti-NoV disinfectants and sanitizers have been performed using surrogate viruses. In this study, NoV virus-like particles (VLPs) were used as a new surrogate for NoVs and a method for evaluating NoV inactivation using them developed. This method is based on morphological changes in VLPs after treatment with sodium hypochlorite. VLP specimens were found to become deformed and degraded in a concentration-dependent manner. Based on these results, the effects of sodium hypochlorite on VLPs were classified into four phases according to morphological changes and number of particles. Using the criteria thus established, the efficacy of ethanol, carbonates and alkali solutions against VLPs was evaluated. Deformation and aggregation of VLPs were observed after treatment with these disinfectants under specific conditions. To determine the degradation mechanism(s), VLPs were examined by SDS-PAGE and immunoblotting after treatment with sodium hypochlorite and ethanol. The band corresponding to the major capsid protein, VP1, was not detected after treatment with sodium hypochlorite at concentrations greater than 500 ppm, but remained after treatment with ethanol. These results suggest that VLPs have excellent potential as a surrogate marker for NoVs and can be used in initial virucidal effectiveness tests to determine the mechanism(s) of chemical agents on NoVs.

Mucosal Antibodies Induced by Intranasal but Not Intramuscular Immunization Block Norovirus GII.4 Virus-Like Particle Receptor Binding.

Noroviruses (NoVs) account for the majority of diagnosed cases of viral acute gastroenteritis worldwide. Virus-like particle (VLP)-based vaccines against NoV are currently under development. Serum antibodies that block the binding of NoV VLPs to histo-blood group antigens, the putative receptors for NoV, correlate with protection against NoV infection. The role of functional mucosal antibodies in protection is largely unknown, even though the intestinal mucosa is the entry port for NoV. Balb/c mice were immunized intramuscularly (IM) or intranasally (IN) with NoV GII.4 VLPs, and systemic and mucosal blocking antibody responses were studied. IN immunization elicited NoV-specific serum and mucosal IgG and IgA antibodies, whereas IM immunized animals completely lacked IgA. Both immunization routes induced similar blocking activity in serum but only IN route generated blocking antibodies in mucosa. The level of IgA in the mucosal (nasal) lavages strongly correlated (r = 0.841) with the blocking activity, suggesting that IgA, but not IgG, is the major NoV blocking antibody on mucosal surfaces. The results indicate that only mucosal immunization route induces the development of functional anti-NoV IgA on mucosal surface.

Norovirus Infection: Replication, Manipulation of Host, and Interaction with the Host Immune Response.

Noroviruses (NoVs) belong to the Caliciviridae family of viruses and are responsible for causing the majority of gastroenteritis outbreaks worldwide. In the past decade, research on NoV biology has intensified because of the discovery of murine NoV and subsequently the first cell culture system and small animal model for NoV replication and pathogenesis. In this review, we discuss the current literature on NoV biology, focusing particularly on NoV replication and the interaction between NoV and the host immune response. Understanding the NoV replication cycle and its interaction with cellular processes and innate immune immunity will help develop molecular targets to control human NoV infection and prevent outbreaks. In addition to the innate immune response, we have documented the current efforts to develop NoV vaccines to control outbreaks.

Human norovirus infection and the acute serum cytokine response.

Noroviruses (NoV) are the most common cause of epidemic gastroenteritis worldwide. The acute immune response to NoV in humans is poorly understood, hindering research on prevention and treatment. To elucidate the acute immune response and test for cytokine predictors of susceptibility to infection, serum samples from two human NoV challenge studies were tested for 16 cytokines. Subjects who became infected (n = 26) were age-matched with subjects who remained uninfected following NoV challenge (n = 26). Samples were tested from prechallenge and days 1-4 post-challenge. Cytokine responses were compared between infected and uninfected groups. Overall, infected individuals exhibited an elevation in T helper type 1 (Th1) and Th2 cytokines, as well as chemokines interleukin (IL)-8 and monocyte chemoattractant protein (MCP-1), compared to uninfected individuals (all P < 0.05). Most cytokines peaked on day 2 post-challenge in infected subjects, and tumour necrosis factor (TNF)-α, IL-8, and IL-10 remained elevated to day 3. The only cytokine elevated significantly among infected subjects to day 4 post-challenge was IL-10 (P = 0.021). Prechallenge cytokine concentrations were not predictive of infection status post-challenge. There were no significant changes in serum cytokines among NoV-challenged subjects who remained uninfected. These results suggest that NoV infection elicits a Th1-type response, with some Th2 activation. Persistent elevation of IL-10 among infected subjects is consistent with activation of adaptive immune responses, such as B cell expansion, as well as down-regulation of Th1 cytokines. This study presents the first comprehensive description of the acute cytokine response to GI.1 NoV in humans.