Molecular epidemiology of norovirus in outbreaks of gastroenteritis in southwest Germany from 2001 to 2004

Curcumin Shows Antiviral Properties against Norovirus

Phytochemicals provide environmentally friendly and relatively inexpensive natural products, which could potentially benefit public health by controlling human norovirus (HuNoV) infection. In this study, 18 different phytochemicals were evaluated for antiviral effects against norovirus using murine norovirus (MNV) as a model for norovirus biology. Among these phytochemicals, curcumin (CCM) was the most potent anti-noroviral phytochemical, followed by resveratrol (RVT). In a cell culture infection model, exposure to CCM or RVT for 3 days reduced infectivity of norovirus by 91% and 80%, respectively. To confirm the antiviral capability of CCM, we further evaluated its antiviral efficacy at various doses (0.25, 0.5, 0.75, 1, and 2 mg/mL) and durations (short-term: 10, 30, 60, and 120 min; long-term: 1, 3, 7, and 14 days). The anti-noroviral effect of CCM was verified to occur in a dose-dependent manner. Additionally, we evaluated the inhibitory effect of each phytochemical on the replication of HuNoV using a HuNoV replicon-bearing cell line (HG23). Neither CCM nor RVT had a strong inhibitory effect on HuNoV replication, which suggests that their antiviral mechanism may involve viral entry or other life cycle stages rather than the replication of viral RNA. Our results demonstrated that CCM may be a promising candidate for development as an anti-noroviral agent to prevent outbreaks of foodborne illness.

Emergence of human caliciviruses among diarrhea cases in southwest China

BACKGROUND

Acute diarrhea is one of the most serious problems in global public health that causes considerable morbidity and mortality worldwide. Human caliciviruses (HuCV) including norovirus (NoV, genogroup GI and GII) and sapovirus (SaV), is a leading cause of acute sporadic diarrhea in individuals across all age groups. However, few studies had been conducted clarifying the characteristics of HuCV in diarrhea cases across all age groups in China. Our study was aimed at assessing the HuCV-related diarrhea burden and NoV genotypes distribution in southwest China.

METHODS

The study was conducted in four hospitals in Kunming city, Yunnan province, from June 2014 to July 2015. Stool specimens were collected from 1,121 diarrhea cases and 319 healthy controls in outpatient departments. Reverse transcription polymerase chain reaction (RT-PCR) was used to detect NoV (GI, GII) and SaV. Sequencing was applied to confirm the three viral infections and phylogenetic analysis was performed to determine their genotypes. A structured questionnaire was used to record the demographic information and clinical symptoms of subjects.

RESULTS

HuCV was detected at an 11.0 % infection rate in 1,121 diarrhea cases and at 3.4 % rate in 319 non-diarrhea subjects (p < 0.0001, OR = 3.5, 95 % CI 1.8-6.5). The prevalence of the NoV genogroup GII and genotype GII.4 in diarrhea cases was significantly higher than that found in healthy controls (p < 0.0001, p = 0.018, respectively). NoV GII (n = 118, 10.5 %) was the most common HuCV subtype in diarrhea cases, followed by SaV (n = 3, 0.3 %) and NoV GI (n = 2, 0.2 %). Of 118 NoV GII strains isolated from diarrhea patients. GII.4 (n = 55, 46.6 %) was the predominant strain, followed by GII.3 (n = 28, 23.7 %), GII.12 (n = 25, 21.2 %), GII.17 (n = 8, 6.8 %), and GII.5 (n = 2, 1.7 %). Of the 55 GII.4 strains, the GII.4 Sydney 2012 variant had absolutely predominant prevalence (n = 52, 94.5 %), followed by the NoV GII.4-2006b variant (n = 3, 5.5 %). The GII.4 Orleans 2009 variant was not found in diarrhea cases of the study.

CONCLUSIONS

NoV GII was the major genogroup and GII.4 was the most predominant strain detected in diarrhea patients. The GII.17 is an emergent variant in sporadic diarrhea and might become the predominant strain in diarrhea cases in the near future. Rapid, accurate detection kits need to be developed to help us find and treat NoV-associated diarrhea in clinical settings in a timely manner.

Epidemics of Norovirus GII.4 Variant in Outbreak Cases in Korea, 2004-2012

Norovirus GII.4 is recognized as a worldwide cause of nonbacterial outbreaks. In particular, the GII.4 variant occurs every 2–3 years according to antigenic variation. The aim of our study was to identify GII.4 variants in outbreaks in Korea during 2004–2012. Partial VP1 sequence of norovirus GII.4-related outbreaks during 2004–2012 was analyzed. The partial VP1 sequence was detected with reverse transcription-polymerase chain reaction, seminested polymerase chain reaction, and nucleotide sequence of 312-314 base pairs for phylogenetic comparison. Nine variants emerged in outbreaks, with the Sydney variant showing predominance recently. This predominance may persist for at least 3 years, although new variants may appear in Korea.

Evolutionary phylodynamics of Korean noroviruses reveals a novel GII.2/GII.10 recombination event

Viral gastroenteritis is the most common causal agent of public health problems worldwide. Noroviruses cause nonbacterial acute gastroenteritis in humans of all ages. In this study, we investigated the occurrence of norovirus infection in children with acute gastroenteritis admitted to university hospitals in South Korea. We also analyzed the genetic diversity of the viruses and identified novel recombination events among the identified viral strains. Of 502 children with acute gastroenteritis admitted to our three hospitals between January 2011 and March 2012, genotyping of human noroviruses was performed in 171 (34%) norovirus-positive samples. Of these samples, 170 (99.5%) were in genogroup II (GII), while only one (0.5%) was in genogroup I (GI). The most common GII strain was the GII.4-2006b variant (n = 96, 56.5%), followed by GII.6 (n = 23, 13.5%), GII.12 (n = 22, 12.9%), GII.3 (n = 20, 11.8%), GII.2 (n = 6, 3.5%), GII.b (n = 2, 1.2%), and GII.10 (n = 1, 0.6%). Potential recombination events (polymerase/capsid) were detected in 39 GII strains (22.9%), and the most frequent genotypes were GII.4/GII.12 (n = 12, 30.8%), GII.4/GII.6 (n = 12, 30.8%), GII.4/GII.3 (n = 8, 20.5%), GII.b/GII.3 (n = 3, 7.7%), GII.16/GII.2 (n = 2, 5.1%), GII.4/GII.2 (n = 1, 2.6%), and GII.2/GII.10 (n = 1, 2.6%). For the first time, a novel GII.2/GII.10 recombination was detected; we also identified the GII.16/GII.2 strain for the first time in South Korea. Our data provided important insights into new recombination events, which may prove valuable for predicting the emergence of circulating norovirus strains with global epidemic potential.

Characterization of novel intergenogroup and intergenotype recombinant noroviruses from central Greece

Noroviruses (NoVs) are a major causative agent of acute gastroenteritis in humans. They are members of the Caliciviridae family and based on the genetic analysis of the RdRp and capsid regions, human NoVs are divided into three genogroups (Gs), GI, GII, and GIV. The three genogroups further segregate into distinct lineages called genotypes. The NoV genus is genetically diverse and recombination of viral RNA is known to depend upon various immunological and intracellular constraints that may allow the emergence of viable recombinants. In this study, three Noroviral strains detected in clinical samples revealed two hitherto unobserved recombination events between GII.9/GII.4 and GII.9/GI.7 genogroups. To our knowledge, these intergenotype and intergenogroup recombination events of GII.9/GII.4 and GII.9/GI.7, in ORF1 and ORF2 genes respectively are reported for the first time and highlight the ongoing evolution of noroviruses.

Clinical characteristics and genetic diversity of noroviruses in adults with acute gastroenteritis in Beijing, China in 2008-2009

Norovirus (NoV) infections that cause acute gastroenteritis are commonly observed during colder months. This study was conducted to investigate the clinical features and molecular epidemiology of NoVs in adult outpatients with acute gastroenteritis in Beijing, China from August 2008 to July 2009. Five hundred nineteen patients were enrolled, their stool specimens were collected, and 136 (26.2%) were positive for NoV. The elderly were found to be more susceptible to NoVs than other age groups. The greatest number of gastroenteritis cases associated with occurred in October. Six GI and eleven GII NoV genotypes were isolated; among these, the GII.4 genotype was most prevalent (70/140 and 50% were the 2006b variant). The elderly were more susceptible to the GII.4 genotype than to other genotypes. Greater numbers of neutrophils in the peripheral blood were observed in the NoV infected group than in uninfected control group. However, the levels of neutrophils and leukocytes in the non-GII.4 patients infected with NoV were higher than those of the GII.4-infected patients. The data highlight the role of NoV as a primary agent responsible for gastroenteritis in adults in Beijing, China.

Bioinformatics analysis of the epitope regions for norovirus capsid protein

BACKGROUND

Norovirus is the major cause of nonbacterial epidemic gastroenteritis, being highly prevalent in both developing and developed countries. Despite of the available monoclonal antibodies (MAbs) for different sub-genogroups, a comprehensive epitope analysis based on various bioinformatics technology is highly desired for future potential antibody development in clinical diagonosis and treatment.

METHODS

A total of 18 full-length human norovirus capsid protein sequences were downloaded from GenBank. Protein modeling was performed with program Modeller 9.9. The modeled 3D structures of capsid protein of norovirus were submitted to the protein antigen spatial epitope prediction webserver (SEPPA) for predicting the possible spatial epitopes with the default threshold. The results were processed using the Biosoftware.

RESULTS

Compared with GI, we found that the GII genogroup had four deletions and two special insertions in the VP1 region. The predicted conformational epitope regions mainly concentrated on N-terminal (1~96), Middle Part (298~305, 355~375) and C-terminal (560~570). We find two common epitope regions on sequences for GI and GII genogroup, and also found an exclusive epitope region for GII genogroup.

CONCLUSIONS

The predicted conformational epitope regions of norovirus VP1 mainly concentrated on N-terminal, Middle Part and C-terminal. We find two common epitope regions on sequences for GI and GII genogroup, and also found an exclusive epitope region for GII genogroup. The overlapping with experimental epitopes indicates the important role of latest computational technologies. With the fast development of computational immunology tools, the bioinformatics pipeline will be more and more critical to vaccine design.

Characterization of norovirus infections in Seoul, Korea

The present study has determined the detection rate of norovirus (NoV) with acute gastroenteritis (AGE) in hospitalized children and describes the molecular epidemiology of NoV circulating in Seoul, Korea. Six hundred and eighty-three (9.8%) of samples were positive for NoV. Of these, the NoV GII genogroup was the most commonly found, with a prevalence of 96.2% (683 of 710). Only 27 samples were positive for the NoV GI genogroup. Ten kinds of GI genotype (GI/1, GI/2, GI/3, GI/4, GI/5, GI/6, GI/7, GI/9, GI/12, and GI/13) and eight kinds of GII genotype (GII/2, GII/3, GII/4, GII/8, GII/14, GII/15, GII/16, and GII/17) were identified in children with AGE during the years 2008-2011.

Towards a rational strategy for monitoring of microbiological quality of ambient waters

Water is one of the main sources of human exposure to microbiological hazards. Although legislation establishes regulatory standards in terms of fecal indicator bacteria to assess the microbiological quality of water, these do not necessarily predict the presence of pathogens such as parasites and viruses. Better surveillance and management strategies are needed to assess the risk of pathogens' waterborne transmission. We established a baseline dataset to characterize river water quality, identify changes over time, and design a rational monitoring strategy. Data from a year-long monthly monitoring campaign of the polluted Arenales River (Argentina), were analyzed to statistically correlate physicochemical and microbiological variables, the seasonal and longitudinal variations of the water quality and determine the similarity between study sites. The measured variables (sixteen) reflected the deterioration in the river quality through the city. Different viruses and parasites found did not correlate with the concentration of total and thermotolerant coliforms. There was significant seasonal variation for temperature, turbidity, conductivity, dissolved oxygen, enterococci, and norovirus. Strong correlations between some variables were found; we selected eight variables (dissolved oxygen, conductivity, turbidity, total and thermotolerant coliforms, Enterococcus, and adenovirus and Microsporidium as viral and parasitological indicators, respectively) for future monitoring. There was similarity between the monitoring locations, which were grouped into four clusters validated by cophenetic correlation and supported by discriminant analysis. This allowed us to reduce the number of sites, from eleven down to five. Sixty seven percent of the total variance and the correlation structure between variables were explained using five principal components. All these analyses led to a new long-term systematic monitoring scheme. A rational monitoring strategy based on the selection of the most suitable monitoring points and of the most significant variables to measure, will result in optimal use of the limited resources available to adequately protect the public and environmental health.

Worldwide molecular epidemiology of norovirus infection

Norovirus (NoV) is recognised as one of the emerging viruses causing infection in humans. It is the leading cause of outbreaks of viral gastro-enteritis worldwide. In children, NoV plays an increasing and important role in enteric infection, apart from rotavirus, especially in the post-rotavirus vaccine era. NoV-infected children usually present with typical clinical manifestations of acute viral gastro-enteritis, including vomiting and watery diarrhoea, and paediatric patients are more liable to have dehydration requiring hospitalisation. Other than these symptoms, severe or atypical complications associated with NoV infection include infantile convulsion, necrotising enterocolitis, and, rarely, disseminated disease involving multiple organs. Although most symptoms of NoV infection are self-limiting, recurrent infection is not uncommon in children as well as in the elderly. The rapid evolution and complex genetic diversity of NoV makes for difficulty in identification, classification and surveillance of the virus. Using molecular biological methods, clearer genetic and molecular features of the circulating NoV are now recognised. The emerging GII.4 genotype is currently responsible for 60-90% of outbreaks worldwide. Rapid transmission of NoV from person-to-person makes the infection difficult to control. In addition to personal hygiene such as hand-washing, prevention of NoV will depend largely on the development of an effective vaccine. Given the rapid evolution of the virus, continued molecular epidemiological surveillance is important.

Virucidal activity of alcohol-based hand rub disinfectants

We investigated the virucidal activity of commercially available alcohol-based hand rub products against coxsackievirus A7, B5, feline calicivirus F9, and human adenovirus type 3, type 7, type 8 using susceptible cell lines, Vero cells, CRFK cells, and A549 cells. Fifteen tested hand rub products were ethanol (EtOH) for disinfection (Japanese Pharmacopoeia Grade), two EtOH-based products, one povidone iode-containing product, one alkyldiaminoethylglycine hydrochloride-containing product, six benzalkonium chloride (BAK)-containing products, and four chlorohexidine gluconate (CHG)-containing products. Some active ingredients (BAK, benzetonium chloride, and CHG) were diluted with EtOH to make 0.5% and 0.2% solutions. Virus inactivation rates were calculated after contact with each hand rub product for 10 or 60 seconds. Of the hand rub products tested, only the povidone iode-based product showed antiviral activity superior to that of EtOH against all the strains. EtOH solutions of active ingredients (0.2% and 0.5%) also showed decreased antiviral activity. In conclusion, antiviral activity of all the commercially available alcohol-based hand rub products except that containing povidone idode was dependent on their active ingredients. The povidone idode-containing hand rub product kept its effectiveness even after the dilution with EtOH. Although alcohol-based hand rub products are convenient and suitable for the control of some microbes, they are not generally recommended for the control of viral infections.

A gastroenteritis outbreak caused by noroviruses in Greece

In June 2006, an outbreak alert regarding cases of acute gastroenteritis in a region in North Eastern Greece (population 100,882 inhabitants), triggered investigations to guide control measures. The outbreak started the first days of June, and peaked in July. A descriptive epidemiological study, a virological characterization of the viral agent identified from cases as well as a phylogenetic analysis was performed. From June 5 to September 3, 2006 (weeks 23–44), 1,640 cases of gastroenteritis (45.2% male and 54.8% female, aged 3 months to 89 years) were reported. The overall attack rate for the period was 16.3 cases/1,000 inhabitants. About 57% of cases observed were under the age of 15 years. nalysis of faecal samples identified Norovirus GII strains. Fifteen different Norovirus GII strains were recorded, presenting a homology of 94.8% (86–97%) to GII strains obtained from GenBank. The long duration of the outbreak suggests an important role of person-to-person transmission, while the emergence of the outbreak was possibly due to contaminated potable water, although no viruses were detected in any tested water samples. This outbreak underscores the need for a national surveillance system for acute non-bacterial gastroenteritis outbreaks.

Norovirus as a foodborne disease hazard

Norovirus (NoV) is the most common cause of infectious gastroenteritis in the world. Gastroenteritis caused by bacterial and parasitic pathogens is commonly linked to food sources, but the link between NoV and contaminated foods has been more difficult to establish. Even when epidemiological information indicates that an outbreak originated with food, the presence of NoV in the suspect product may not be confirmed. If food is found to contain a common strain of NoV that circulates widely in the community, it is not possible to use strain typing to link the contamination to patient cases. Although food is certainly implicated in NoV spread, there are additional person-to-person and fomite transmission routes that have been shown to be important. NoV has an extremely low infectious dose, is stable in the environment, and resists disinfection. Cell culture methods are not available, so viability cannot be determined. Finally, many NoV outbreaks originate with when an infected food handler contaminates ready-to-eat food, which can be interpreted as foodborne or person-to-person transmission. This review will discuss both the physical characteristics of NoVs and the available epidemiological information with particular reference to the role of foods in NoV transmission.

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.

Surveillance of norovirus infections in the state of Rio De Janeiro, Brazil 2005-2008

A 4-year (2005-2008) norovirus (NoV) surveillance study was conducted in the state of Rio Janeiro, Brazil, to demonstrate the role of these viruses in outbreaks and sporadic cases of acute gastroenteritis. A cohort of 1,687 fecal samples was obtained from patients with gastroenteritis; 324 were rotavirus-positive. Of the remainder 1,363 rotavirus-negative samples, 1,087 samples were tested for NoV RNA in this study. The study enrolled 267 outpatients from Municipal Public Health Centers and 820 inpatients, whose samples were obtained by active surveillance in Public Hospitals. Fecal samples were tested by reverse transcription (RT) followed by polymerase chain reaction (PCR) using the MON 431-434 set of degenerate primers for NoV GI and GII detection, and there were 35.1% (381/1,087) positive samples for NoV, consisting of 30.2% (248/820) and 49.8% (133/267) from inpatient and outpatient, respectively. Children infected by NoV had significantly more frequent mucus in feces, vomiting and fever. No seasonal pattern in NoV infections was observed in patients admitted to hospital; however, two peaks of NoV infections were observed from ambulatory cases, suggesting that there was an occurrence of outbreaks in those time periods. Molecular characterization revealed GII to be the most prevalent genogroup, totaling 96.3% (104/108) of all sequences analyzed, and GII.4 was the genotype detected most frequently (80.7%), followed by GII.6, 3, 14, 7, and 8. Two GI strains, GI.2 and GI.3, were also observed. The number of outbreaks and sporadic cases described in this study highlights the need to implement diagnosis of NoV in surveillance laboratories.

Inadequately treated wastewater as a source of human enteric viruses in the environment

Human enteric viruses are causative agents in both developed and developing countries of many non-bacterial gastrointestinal tract infections, respiratory tract infections, conjunctivitis, hepatitis and other more serious infections with high morbidity and mortality in immunocompromised individuals such as meningitis, encephalitis and paralysis. Human enteric viruses infect and replicate in the gastrointestinal tract of their hosts and are released in large quantities in the stools of infected individuals. The discharge of inadequately treated sewage effluents is the most common source of enteric viral pathogens in aquatic environments. Due to the lack of correlation between the inactivation rates of bacterial indicators and viral pathogens, human adenoviruses have been proposed as a suitable index for the effective indication of viral contaminants in aquatic environments. This paper reviews the major genera of pathogenic human enteric viruses, their pathogenicity and epidemiology, as well as the role of wastewater effluents in their transmission.

The Prevalence of Norovirus in returning international travelers with diarrhea

Background

There is a high incidence of diarrhea in traveling populations. Norovirus (NV) infection is a common cause of diarrhea and is associated with 7% of all diarrhea related deaths in the US. However, data on the overall prevalence of NV infection in traveling populations is limited. Furthermore, the prevalence of NV amongst travelers returning to Europe has not been reported. This study determined the prevalence of NV among international travelers returning to Germany from over 50 destinations in and outside Europe.

Methods

Stool samples of a total of 104 patients with a recent (< 14days) history of international travel (55 male, mean age 37 yrs.) were tested for the presence of NV genogroup (GG) I and II infection using a sensitive and well established quantitative RT PCR method. 57 patients experienced diarrhea at the time of presentation at the Department of Infectious Diseases & Tropical Medicine. The remaining 47 patients had no experience of diarrhea or other gastrointestinal symptoms for at least 14 days prior to their date of presentation at our institute.

Results

In our cohort, NV infection was detected in 15.7% of returning travelers with diarrhea. The closer to the date of return symptoms appeared, the higher the incidence of NV, ranging as high as 21.2% within the first four days after return.

Conclusions

In our cohort, NV infection was shown to be frequent among returning travelers especially in those with diarrhea, with over 1/5 of diarrhea patients tested positive for NV within the first four days after their return to Germany. Due to this prevalence, routine testing for NV infection and hygienic precautions may be warranted in this group. This is especially applicable to patients at an increased risk of spreading the disease, such as healthcare workers, teachers or food-handlers.

Epidemiological and clinical features of norovirus gastroenteritis in outbreaks: a population-based study

Noroviruses are the most frequent cause of acute gastroenteritis in the community. In Catalonia, it is not clear how this type of viral gastroenteritis is evolving, and the objective of this prospective population-based study was to describe the incidence and epidemiological and clinical features of outbreaks of acute gastroenteritis due to norovirus in Catalonia between October 2004 and October 2005. Incidence rates were calculated using the estimated population of Catalonia in 2005. For each outbreak, the mode of transmission, the number of persons affected, demographic variables, clinical presentation, the date and time of onset of symptoms and the duration of symptoms, physician visits and hospitalizations were collected. Sixty viral outbreaks affecting 1791 people were identified, with no distinct seasonality. The mean number of outbreaks per month was 4.6. The global incidence was 24.6 per 100 000 person-years. The incidence was higher in women (25.7 per 100 000 person-years) and in the 5-11 years (52.4 per 100 000 person-years) and > or =65 years (42.4 per 100 000 person-years) age groups. The prevalence of vomiting, abdominal pain and general malaise was higher in children and adolescents, whereas the prevalence of diarrhoea and myalgia was higher in adults. These results suggest that norovirus infection has an important public health impact in Catalonia and that prevention strategies should be designed and implemented.

Viral shape-shifting: norovirus evasion of the human immune system

Noroviruses are a major cause of gastroenteritis, and there are currently no vaccines or antiviral treatments available to treat or prevent the >260 million gastroenteritis cases that are reported globally each year. Noroviruses have proven difficult to work with in the laboratory owing to the lack of cell culture systems and animal models, and therefore little is known about the pathogenesis caused by this virus, which has hampered the development of efficacious therapeutics.

The norovirus family contains two genogroups (GI and GII) that are most commonly associated with enteric disease in humans, and these genogroups contain more than 25 different genotypes that account for most human norovirus cases. However, outbreaks caused by the GII.4 genotype occur much more frequently than those caused by other genotypes in the GII genogroup, and GI outbreaks occur even less frequently. Although the majority of norovirus outbreaks are caused by the GII.4 genotype, the molecular and biological factors that regulate this disease burden are only partially understood.

The GII.4 genotype seems to operate in a similar fashion as influenza virus, whereby evolution of novel immune escape variants allows the virus to escape the predominant memory immune response. By contrast, the prototypic GI.1 noroviruses have remained relatively static over the same time period, evolving variants with identical histo-blood group antigen binding capabilities and similar antigenic properties. The molecular mechanisms governing differential evolution patterns remain a key mystery in the norovirus field.

Immunity against noroviruses has been difficult to assess owing to the complex effects of host pre-exposure histories and differential host susceptibility, which is correlated with blood group and secretor status. However, recent work has suggested that the GI and GII genogroups may use different mechanisms to escape immunological memory and that this is perhaps directly related to the plasticity of and complex evolutionary-related sequence information encoded in the P2 subdomain of the capsid protein.

The GII genogroup contains more amino acid sequence in the P2 subdomain, which may allow increased capsid plasticity and a tolerance for more amino acid variation or insertions and deletions. This would provide a larger repertoire of sequence targets for natural selection and adaptation to complex environmental selection processes, like herd immunity. By contrast, the GI genogroup contains less sequence information with more conserved, surface-exposed residues that are probably recognized by homologous antibodies as well as antibodies generated against heterologous GI strains. Thus, complex patterns of GI pre-exposure history, antibody cross reactivity and original antigenic sin may facilitate secondary infections of GI strains, whereas antigenic drift and receptor switching allow GII noroviruses, especially GII.4 viruses, to persist in human populations.

Noroviruses are the most common cause of food-borne gastroenteritis worldwide; however, the development of effective vaccines and antiviral therapies has proved to be challenging. In this Review, Baric and colleagues discuss the molecular and structural mechanisms underlying the persistence of noroviruses in human populations.

Noroviruses are the most common cause of food-borne gastroenteritis worldwide, and explosive outbreaks frequently occur in community settings, where the virus can immobilize large numbers of infected individuals for 24–48 hours, making the development of effective vaccines and antiviral therapies a priority. However, several challenges have hampered therapeutic design, including: the limitations of cell culture and small-animal model systems; the complex effects of host pre-exposure histories; differential host susceptibility, which is correlated with blood group and secretor status; and the evolution of novel immune escape variants. In this Review, we discuss the molecular and structural mechanisms that facilitate the persistence of noroviruses in human populations.

Characterization of ozone disinfection of murine norovirus

Despite the importance of human noroviruses (NoVs) in public health, little information concerning the effectiveness of ozone against NoVs is available. We determined the efficacy of ozone disinfection using murine norovirus (MNV) as a surrogate of human NoV. MNV in ozone demand-free buffer was exposed to a predetermined dose of ozone at two different pHs and temperatures. The virus remaining in the solution was analyzed by plaque assay, real-time TaqMan reverse transcriptase PCR (RT-PCR) (short template), and long-template conventional RT-PCR. Under all conditions, more than 99% of the MNV was inactivated by ozone at 1 mg/liter within 2 min. Both RT-PCR assays significantly underestimated the inactivation of MNV, compared with that measured by plaque assay. Our results indicate that NoV may be more resistant to ozone than has been previously reported. Nevertheless, proper ozone disinfection practices can be used to easily control its transmission in water.

Norovirus infections in preterm infants: wide variety of clinical courses

BACKGROUND

Norovirus is an important cause of nonbacterial acute gastroenteritis in all ages. Atypical courses are described. Clinical symptoms are diarrhea, vomiting, nausea, abdominal cramps, fever and malaise. Apart from three recent short reports we describe for the first time an outbreak of norovirus in a tertiary Neonatal Intensive Care Unit.

FINDINGS

The typical symptoms of norovirus infection are in part also seen in premature born infants but with a different pattern and a huge variety of clinical courses. Vomiting is not the main symptom of norovirus infection in premature infants but distended abdomen and other symptoms such as apnea, gastric remainders or sepsis like appearance. The course in premature born patients could be explained by an immunocompromised mice model. Extensive hygienic measures were necessary to control the outbreak without closing the Neonatal Intensive Care Unit.

CONCLUSION

Norovirus infection in premature infants shows an impressive pattern of a wide variety of clinical courses. Only the consequent use of different hygienic pattern can lead to elimination of norovirus.

Detection of a novel intergenogroup recombinant Norovirus from Kolkata, India

Mutation and recombination are recognized as important driving forces of evolution among RNA viruses. An intergenogroup recombinant norovirus strain [Hu/Kol/NLV/L8775/AB290150/2006/India] was detected in the faecal specimen of a 17 year old male, who had suffered from acute watery diarrhea and severe dehydration. Sequence analysis confirmed that this novel recombinant strain had a polymerase gene fragment that closely resembled a Norovirus (NoV) genogroup-I genotype-3 virus (HuCV/NLV/GI.3/VA98115/AY038598/1998/USA) and a capsid gene resembling NoV genogroup-II genotype-4 virus (NoV/Hu/GII.4/Terneuzen70/EF126964/2006/NL). The crossing over and recombination was observed at nucleotide (nt) 790 of NoV GI VA98115 strain and nt808 of NoV GII Terneuzen70 strain. In both parent strains conserved nucleotide sequence and hairpin structure (DNA secondary structure) were reported at the junction point of ORF1 and ORF2, exhibiting the mechanism of recombination in these viruses. Thus this novel recombinant NoV is another step in evolution among NoVs, indicating that constant surveillance is important to successfully monitor emergence of these strains.

Detection and characterization of sapoviruses in outbreaks of gastroenteritis in southwest Germany

BACKGROUND

Sapovirus (SV) has been reported from many countries as one of the major causes of gastroenteritis in infants, but its importance for a broader age range is not well appreciated. While previous studies in our regional laboratory and other parts of Germany have identified Norovirus (NV) as a major cause of gastroenteritis in Germany, the prevalence of SV has not been recorded.

OBJECTIVES

To investigate the prevalence of SV in outbreaks of gastroenteritis in Baden-Württemberg, Germany.

STUDY DESIGN

Stool specimens from 34 outbreaks of gastroenteritis collected in Baden-Württemberg, Germany in 2002 and 2003, which tested negative for other enteric pathogens were tested for SV by RT-PCR. Positive samples were sequenced and typed using phylogenetic analysis.

RESULTS

SV was identified in two of 157 (1.3%) specimens. These two viruses belonged to different genotypes of SV and had a nucleotide similarity of only 57%.

CONCLUSIONS

SV circulates within the study area, but is not an important cause of gastroenteritis in the area.

Recombinant norovirus implicated in gastroenteritis outbreaks in Hiroshima Prefecture, Japan

Norovirus (NoV) is a major etiological agent of acute gastroenteritis outbreaks worldwide. A total of 314 fecal specimens collected from patients of 39 NoV gastroenteritis outbreaks in Hiroshima Prefecture, Japan, between December 2001 and April 2006 were tested for the occurrence of recombinant NoVs. Sixteen genotypes (GI/1, GI/2, GI/4, GI/7, GI/8, GI/11, GI/14, GII/2, GII/3, GII/4, GII/5, GII/6, GII/8, GII/12, GII/14, and GII/untypeable) were detected in the 39 outbreaks based on capsid sequences and GII/4 was predominant recently. Twelve strains detected in 11 (28.2%) of the 39 outbreaks were suspected to be recombinants by using Simplot and Recco analyses and five recombinant genotypes, GII/4-GII/12 (five strains), GIIb-GII/3 (four strains), GII/4-GII/2 (one strain), GII/4-GII/14 (one strain), and GI/2-GI/8 (one strain), were identified based on RNA-dependent RNA polymerase and capsid sequences. None of the strains genotyped as GII/4 based on the capsid sequence was identified as a recombinant. The putative recombination points in the recombinant strains were placed either upstream or downstream of the open reading frame (ORF) 1 and ORF2 overlap. The present study indicates the following: (a) recombination among ORFs is common in nature, (b) the involvement of recombinant NoVs in gastroenteritis outbreaks is extensive even in a local area such as Hiroshima Prefecture, Japan, and (c) the conserved region (ORF1 and ORF2 overlap) has a meaningful function against the recombination event.

Acute infantile gastroenteritis associated with human enteric viruses in Tunisia

This prospective study, conducted from January 2003 to June 2005, investigated the incidence and the clinical role of various enteric viruses responsible for infantile gastroenteritis in 632 Tunisian children presenting in dispensaries (380 children) or hospitalized (252 children) for acute diarrhea. At least one enteric virus was found in each of 276 samples (43.7%). A single pathogen was observed in 234 samples, and mixed infections were found in 42 samples. In terms of frequency, rotavirus and norovirus were detected in 22.5 and 17.4% of the samples, respectively, followed by astrovirus (4.1%), Aichi virus (3.5%), adenovirus types 40 and 41 (2.7%), and sapovirus (1.0%). The seasonal distribution of viral gastroenteritis showed a winter peak but also an unusual peak from May to September. The severity of the diarrhea was evaluated for hospitalized infants. No significant differences were observed between rotavirus and norovirus infections with regard to the incidence and the clinical severity of the disease, especially in dehydration.

Molecular detection and characterization of gastroenteritis viruses occurring naturally in the stream waters of Manaus, central Amazonia, Brazil

To assess the presence of the four main viruses responsible for human acute gastroenteritis in a hydrographic network impacted by a disordered urbanization process, a 1-year study was performed involving water sample collection from streams in the hydrographic basin surrounding the city of Manaus, Amazonas, Brazil. Thirteen surface water sample collection sites, including different areas of human settlement characterized as urban, rural, and primary forest, located in the Tarumã-Açu, São Raimundo, Educandos, and Puraquequara microbasins, were defined with a global positioning system. At least one virus was detected in 59.6% (31/52) of the water samples analyzed, and rotavirus was the most frequent (44.2%), followed by human adenovirus (30.8%), human astrovirus (15.4%), and norovirus (5.8%). The viral contamination observed mainly in the urban streams reflected the presence of a local high-density population and indicated the gastroenteritis burden from pathogenic viruses in the water, principally due to recreational activities such as bathing. The presence of viral genomes in areas where fecal contamination was not demonstrated by bacterial indicators suggests prolonged virus persistence in aquatic environments and emphasizes the enteric virus group as the most reliable for environmental monitoring.

Phylogenetic analysis of norovirus isolates involved in some Canadian gastroenteritis outbreaks in 2004 and 2005

Noroviruses are recognized as the most common cause of nonbacterial gastroenteritis worldwide. In this study, we investigated the molecular epidemiology of noroviral isolates in Canada from 2004 to 2005 by sequencing the RNA polymerase gene and capsid N-terminal/shell (N/S) domain. Norovirus genogroups I and II were thus found to have co-circulated in Canada during the studied period, with a higher incidence of genogroup II (95.7%). The GII-4 or Lordsdale subgroup was the predominant genotype, suggesting that norovirus genogroup II is the major cause of viral gastroenteritis in Canada, as it is in many other countries. Phylogenetic analyses of the RNA polymerase gene and the capsid N/S domain indicated different genotypes for 2 strains, suggesting probable genetic recombination. Sequencing of the norovirus polymerase gene may reflect actual classification but should be supported by sequence information obtained from the capsid gene.

Longitudinal molecular epidemiological analysis of feline calicivirus infection in an animal shelter: a model for investigating calicivirus transmission within high-density, high-turnover populations

The control of outbreaks of calicivirus infection in high-density, high-throughput populations is a challenge to both human and veterinary medicine. In such populations, the prevalence of infection is, in part, dependent on the levels of biosecurity and how this affects virus transmission. Here we show how longitudinal analysis of feline calicivirus (FCV) infection in an animal rescue shelter can be used as a model to examine the dynamics of calicivirus transmission and evolution in such environments. FCV was isolated from 33 of 116 cats sampled over a 15-month period (overall prevalence, 28%). Sequence analysis of the immunodominant variable regions of the viral capsid gene identified 16 strains circulating in the shelter, with no single strain appearing to predominate. The majority of these strains were introduced into the shelter from the community and did not appear to be transmitted within the population. However, for three of these strains, putative transmission events within the shelter were identified. The rates of evolution within hypervariable regions of the FCV capsid gene in individual cats ranged from 0.05 to 1.4% per week, with the highest rates generally being found in animals that either acquired the virus while in the shelter or were undergoing acute infection. These data suggest that despite the high prevalence and presence of multiple strains of FCV within the shelter, the spread of such pathogens may be restricted by various control measures, including good hygiene and biosecurity.

Evaluation of immunochromatography tests for detection of rotavirus and norovirus among Vietnamese children with acute gastroenteritis and the emergence of a novel norovirus GII.4 variant

A prospective study was conducted to evaluate two immunochromatography (ICG) tests for detection of group A rotavirus and norovirus GII, the commercial Dipstick 'Eiken' Rota kit (SA Scientific, USA) and the NV IC-1 stick (Immuno-Probe, Japan). Polymerase chain reaction (PCR) with specific primer pairs (Beg9 and VP7-1', for group A rotavirus; COG2F and G2SKR, for norovirus GII) was used as the reference method. The results of ICG tests were compared with those of reference method. The sensitivity, specificity and agreement between ICG tests and PCR were 87.8%, 93.3% and 89.4%, respectively, for rotavirus ICG test; and 73.7%, 100% and 95.2%, respectively, for norovirus ICG test. The immunochromatography assay for norovirus used in this study could detect not only common noroviruses, but also a novel norovirus GII.4 variant, which emerged in Ho Chi Minh City in 2006. Immunochromatography tests are easy, rapid and useful assays for detection of rotavirus and norovirus among pediatric patients with acute gastroenteritis in Vietnam.

Comparison of the sensitivities of noroviruses and feline calicivirus to chemical disinfection under field-like conditions

Noroviruses (NV), in the family Caliciviridae, are an important cause of gastroenteritis in humans worldwide. Measures for prevention and control of NV dissemination are therefore necessary to ensure public safety. The abilities of an organic acid (Venno Vet 1 Super), an aldehyde (Venno FF Super), a halogen compound (sodium hypochlorite solution), and a peroxide (Oxystrong FG) to inactivate feline calicivirus (FCV), a cultivable virus surrogate for NV, were studied. Molecular protocols were then used for the comparative evaluation of disinfectant efficacies against NV and FCV, which were tested by reproducing NV field conditions, using human fecal material as a protein load. Generally, disinfectant efficacy was strongly reduced by the organic impurities (feces) used during tests. All disinfectants, except the aldehyde, were effective on FCV, as measured by cell culture and reverse transcription-PCR (RT-PCR), with inactivation levels of >or=99.9%. The glutaraldehyde-based compound failed to adequately inactivate FCV according to RT-PCR results, although the infectivity in cell culture was completely abolished. Similar inactivation levels were achieved with NV, but generally NV appeared more resistant than FCV, and consequently, the suitability of FCV as a model for NV should be considered with caution. In conclusion, according to RT-PCR results, 5% Venno Vet 1 Super, 1% Oxystrong FG, and not less than 2% Venno FF Super, with a contact time of 1 h, and 1% sodium hypochlorite, with 6,000 ppm of free chlorine and a contact time of 15 min, are required for safe disinfection when a calicivirus-related outbreak is suspected.

Prevalence and molecular epidemiology of noroviruses in hospitalized children with acute gastroenteritis in Rio de Janeiro, Brazil, 2004

BACKGROUND

The role of noroviruses (NoV) as a cause of gastroenteritis outbreaks is well documented; however, the importance of NoV infections in hospitalized children is not well established. The aim of this study was to determine the prevalence and the genetic diversity of NoV in hospitalized children.

METHODS

Three-hundred eighteen fecal samples were collected from January to December 2004, from children with acute gastroenteritis in 3 public hospitals in Rio de Janeiro, Brazil. The prevalence and genetic diversity of NoV was carried out by using genome amplification and sequencing of polymerase and capsid genes.

RESULTS

NoV infections were detected in 65 (20%) of the samples, of which 11 (4%) were mixed infections with rotavirus. Infants up to 1-year-old were the most affected and a peak of virus detection was observed in autumn and spring seasons. Dehydration and diarrhea were the inclusion criterion; coughing (51%), vomiting (33%), and fever (22%) were the main clinical manifestations. Phylogenetic analysis showed that Genogroup II and GII/4 were prevalent. Two potential recombinant strains based in the different clustering pattern were observed.

CONCLUSIONS

This study demonstrated the importance of NoV infections causing severe acute gastroenteritis in hospitalized children in Rio de Janeiro, Brazil. Molecular epidemiology surveillance determining the circulation pattern of different genotypes and recombinant strains is helpful for designing prevention strategies of NoV transmission in children. Studies concerning the prevalence and the molecular epidemiology of gastroenteric viruses in hospitalized children are particularly important to evaluate the impact of the rotavirus vaccine in Brazil.

Atypical norovirus epidemic in Hong Kong during summer of 2006 caused by a new genogroup II/4 variant

An atypically high level of norovirus activity was noticed in Hong Kong beginning in early May 2006. A study was carried out to investigate whether this was caused by a new norovirus variant. Epidemiological data including monthly positivity rates and the numbers of outbreaks per month from January to July 2006 were analyzed and compared to those from 2002 to 2005. In a comparison with the epidemiological data from 2001 to 2005, an atypical peak of norovirus-associated gastroenteritis outbreak was observed beginning in May 2006, concurring with a striking increase in norovirus activity. Most of the outbreaks (>60%) were located in homes for the elderly. Phylogenetic analysis for both RdRp and 5' capsid regions showed that this epidemic was caused by a new genogroup II/4 variant. This variant was genetically distinct from the predominant variants of 2002 and 2004 but was closely related to one of the 95/96-subset variants which caused an epidemic in Hong Kong in 2001, suggesting that the 95/96 subset may be starting to recirculate.

Detection of the norovirus variants GGII.4 hunter and GGIIb/hilversum in Italian children with gastroenteritis

Noroviruses (NoVs) are important enteric pathogens of humans. Although they exhibit an impressive genetic diversity, few NoV strains appear to predominate worldwide. Limited epidemiological data are available on NoV gastroenteritis in Italy. In this study, we assessed the prevalence of human NoV in Italian children with gastroenteritis by using a reverse-transcription nested polymerase chain reaction (RT-PCR) assay specific for the RNA-dependent RNA polymerase (RdRp) on faecal samples collected throughout the 2004 surveillance activity in Palermo, Italy. NoVs were detected in 47% of the stool samples obtained from children <5 years age, admitted to hospital with acute non-bacterial gastroenteritis. A selection of strains was further analyzed by partial sequence analysis of the RdRp gene. The strains were characterized as genogroup (GG) II and clustered into two distinct virus populations that resembled the emerging European GGIIb/Hilversum strains and the Australian Hunter GGII.4 strains. A temporal pattern of distribution of the two NoV strains was observed which was consistent with an independent circulation of two separate strains in the local population. Based on this 1-year study we concluded that NoVs were a diffuse cause of sporadic cases of acute childhood gastroenteritis and that strains of global epidemiological relevance were circulating in Palermo, Italy in 2004.