Human caliciviruses and pediatric gastroenteritis

Nucleic Acid Detection through RNA-Guided Protease Activity in Type III-E CRISPR-Cas Systems

RNA-guided protease activity was recently discovered in the type III-E CRISPR-Cas systems (Craspase), providing a novel platform for engineering a protein probe instead of the commonly used nucleic acid probe in nucleic acid detection assays. Here, by adapting a fluorescence readout technique using the affinity- and fluorescent protein dual-tagged Csx30 protein substrate, we have established an assay monitoring Csx30 cleavage by target ssRNA-activated Craspase. Four Craspase-based nucleic acid detection systems for genes from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), norovirus, and the influenza virus (IFV) were reconstituted with demonstrated specificity. The assay could reliably detect target ssRNAs at concentrations down to 25 pM, which could be further improved approximately 15 000-fold (ca. 2 fM) by incorporating a recombinase polymerase isothermal preamplification step. Importantly, the species-specific substrate cleavage specificity of Craspase enabled multiplexed diagnosis, as demonstrated by the reconstituted composite systems for simultaneous detection of two genes from the same virus (SARS-CoV-2, spike and nsp12) or two types of viruses (SARS-CoV-2 and IFV). The assay could be further expanded by diversifying the fluorescent tags in the substrate and including Craspase systems from various species, thus potentially providing an easily adaptable platform for clinical diagnosis.

Genetic diversity of norovirus associated with outbreaks in school children with acute gastroenteritis in Changzhou, China, 2018-2019

OBJECTIVE

Norovirus is one of the major causes of outbreaks and sporadic cases of acute gastroenteritis in school children. Obtaining local genotype diversity information regarding norovirus is important for developing and evaluating prevention strategies of the transmission of this virus in school children.

METHODS

Clinical specimens, obtained from the routine acute gastroenteritis surveillance network from 2018 to 2019, were primarily tested using commercial real-time PCR Kit. Samples with Ct value less than 25 were selected and used for complete genome sequencing and those with Ct value between 25 and 30 were selected and used for he partial VP1 and RdRp regions sequencing. Phylogenetic trees of the viral genome were constructed by using the neighbor-joining method with bootstrap analysis of 1,000 replicates in MEGA 6.0 RESULTS: Epidemiological surveillance of acute intestinal infections (n=384) showed high-level detection (73.18%) of human norovirus in school endemic acute gastroenteritis events in Changzhou, with obvious epidemic characteristics in autumn and winter. Through genotyping, it was found that 93.12% of norovirus were GII, including GII.2, GII.3, GII.4, GII.6, GII.7 and GII.17. By October 2019, two norovirus genotypes, GII.4[P31] and GII.17[P17], became the preponderant epidemic strains. Phylogenetic analysis of the new GII.17[P17] complete genomes showed close relationship with Miyagi strain identified in Japan in 2015, and GII.4[P31] showed close relationship with Jinan strain indentified in China in 2017.

CONCLUSION

The study highlights the emerging role of GII.4[P31] and GII.17[P17] in causing endemic acute gastroenteritis outbreaks at school children, in Changzhou, China in 2019. This article is protected by copyright. All rights reserved.

Causes of acute gastroenteritis in Korean children between 2004 and 2019

Since the 2000s, the major causes of acute gastroenteritis in children in Korea have been identified by classifying the pathogens into viruses, bacteria, and protozoa. For viruses, the detection rate is 20%-30%, and norovirus is being increasingly detected to account for the majority of viral gastroenteritis cases. In addition, despite the dissemination of the rotavirus vaccine, many rotavirus infections persist, and its seasonal distribution is changing. The detection rate of bacterial pathogens is 3%- 20%, with Escherichia coli and Salmonella spp. infections being the most common, while the incidences of Bacillus cereus and Campylobacter spp. infections are gradually increasing. Owing to intermittent outbreaks of gastroenteritis caused by individual bacteria as well as the inflow of causative bacteria, such as E. coli, Vibrio spp., and Campylobacter spp., from overseas, continuous surveillance of and research into the characteristics and serotypes of each bacterium are needed.

Inhibition of human norovirus by a viral polymerase inhibitor in the B cell culture system and in the mouse model

The recently developed human norovirus (HuNoV) B cell culture and mouse models hold promise for drug discovery and development but their suitability for antiviral studies has not been assessed. We demonstrate the inhibitory effect of the nucleoside analogue 2'-C-methylcytidine (2CMC) on HuNoV replication in the human B cell BJAB cell line and in Balb/c Rag/gamma chain-deficient (Rag-γc(-/-)) mice. These data suggest the applicability of both models for future study and development of antiviral drugs for the treatment of HuNoV infections.

Prevalence and Genetic Diversity of Enteric Viruses in Children with Diarrhea in Ouagadougou, Burkina Faso

Enteric viruses are a major cause of diarrhea in children, especially those under five years old. Identifying the viral agents is critical to the development of effective preventive measures. This study aimed to determine the prevalence and genetic diversity of common enteric viruses in children under five years old in Burkina Faso. Stool samples from children with (n = 263) and without (n = 50) diarrhea disorders were collected in Ouagadougou, Burkina Faso from November 2011 to September 2012. Rotavirus, norovirus, sapovirus, astrovirus, adenovirus and Aichivirus A were detected using real-time or end-point (RT-)PCR. Rotavirus strains were G and P genotyped by multiplex RT-PCR and other viral strains were characterized by sequencing of viral subgenomic segements. At least one viral agent was detected in 85.6% and 72% of the symptomatic and asymptomatic patients, respectively. Rotavirus (63.5%), adenovirus (31.2%) and genogroup II norovirus (18.2%) were the most prevalent viruses in symptomatic patients, but only rotavirus and genogroup II norovirus were significantly associated with diarrhea (OR: 7.9, 95%CI: 3.7-17; OR: 3.5, 95%CI: 1-11.7, respectively). Sapovirus (10.3%), astrovirus (4.9%), genogroup I norovirus (2.7%) and Aichivirus A (0.8%) were less prevalent. The predominant genotype of rotavirus was G9P[8] (36.5%), and the predominant norovirus strain was GII.4 variant 2012 (71.4%). Among sapovirus, the genogroup II (87.5%) predominated. Astrovirus type 1 (41.7%) was the most frequent astrovirus identified. Aichivirus A belonged to the three genotypes (A, B and C). Enteric adenoviruses type 40 and 41 were identified in 10.2% and 5.1% respectively. Several cases of co-infections were detected. The results highlight the high prevalence and the high diversity of enteric viruses in Burkinabe children.

Gastrointestinal Infections

Establishing a specific etiology for gastrointestinal infections can be challenging because of the common clinical features and wide variety of causative microorganisms. In many cases, the etiologic agent cannot be determined using traditional diagnostic methods and may result in unnecessary antibiotic use or prolonged periods of illness. Molecular tests provide many advantages over traditional laboratory methods but, with the exception of a few analytes, are still largely in the developmental phase for gastrointestinal pathogens and are not widely used. The main advantages of molecular tests include increased sensitivity and the ability to detect agents which will not grow in culture. To test for all possible gastrointestinal pathogens at one time would require a large panel that would include a variety of bacterial, viral and parasitic agents. Challenges inherent in developing diagnostic molecular panels include ensuring that all variants of a particular microorganism can be detected as well as the rapid evolution of pathogens. In this chapter, the diagnostic merit of molecular tests as well as available tests will be presented for the major groups of gastrointestinal pathogens.

Association of host, agent and environment characteristics and the duration of incubation and symptomatic periods of norovirus gastroenteritis

We analysed the reported duration of incubation and symptomatic periods of norovirus for a dataset of 1022 outbreaks, 64 of which reported data on the average incubation period and 87 on the average symptomatic period. We found the mean and median incubation periods for norovirus to be 32·8 [95% confidence interval (CI) 30·9-34·6] hours and 33·5 (95% CI 32·0-34·0) hours, respectively. For the symptomatic period we found the mean and median to be 44·2 (95% CI 38·9-50·7) hours and 43·0 (95% CI 36·0-48·0) hours, respectively. We further investigated how these average periods were associated with several reported host, agent and environmental characteristics. We did not find any strong, biologically meaningful associations between the duration of incubation or symptomatic periods and the reported host, pathogen and environmental characteristics. Overall, we found that the distributions of incubation and symptomatic periods for norovirus infections are fairly constant and showed little differences with regard to the host, pathogen and environmental characteristics we analysed.

Norovirus GII.4 antibodies in breast milk and serum samples: their role preventing virus-like particles binding to their receptors

BACKGROUND

Norovirus GII.4 genotype is a leading cause of nonbacterial gastroenteritis in infants. Effective vaccines against noroviruses are not yet available, enhancing the interest of the protection mechanisms elicited by breast milk that may contain norovirus-specific antibodies and histo-blood group antigens. The aims of our study were to analyze norovirus GII.4-specific antibodies in breast milk and serum and to assess their blocking activity on recombinant norovirus virus-like particles (VLPs) binding to saliva.

METHODS

Mature milk and serum from 108 mothers were analyzed for specific IgA to norovirus GII.4-2006b and for their blocking activity on the binding of norovirus GII.4-2006b VLPs to fucosyltransferase FUT2-positive and negative saliva. Norovirus GII.4-2006b-specific IgG antibodies were also analyzed in serum samples.

RESULTS

Higher specific IgA titers were detected in mature milk (75%) than in serum samples (62%), showing a correlation between both results (ρ = 0.427, P = 0.000). However, only 56.3% of the serum samples contained norovirus-specific IgG. Almost all mature milk samples (99.1%) inhibited the binding of norovirus VLPs to FUT2-negative saliva; however, only 25% did so to FUT2-positive saliva (P = 0.000). Ninety percent of serum samples inhibited the binding of norovirus VLPs to FUT2-negative saliva.

CONCLUSIONS

Breast milk inhibits norovirus GII.4-2006b VLPs binding to receptors in saliva, and anti-norovirus IgA antibodies are only partly responsible for this activity. The FUT2 status of the receptor seems to be a strong predictor of this effect, but more studies to ascertain the participation of histo-blood group antigens in the protection against norovirus infections elicited by breast milk are required.

Predominance of norovirus and sapovirus in Nicaragua after implementation of universal rotavirus vaccination

Background

Despite significant reduction of rotavirus (RV) infections following implementation of RotaTeq vaccination in Nicaragua, a large burden of patients with diarrhea persists.

Methods

We conducted a community- and hospital-based study of the burden of RV, norovirus (NV) and sapovirus (SV) infections as cause of sporadic acute gastroenteritis (GE) among 330 children ≤ 5 years of age between September 2009 and October 2010 in two major cities of Nicaragua with a RotaTeq coverage rate of 95%.

Results

We found that NV, SV and RV infections altogether accounted for 45% of cases of GE. Notably, NV was found in 24% (79/330) of the children, followed by SV (17%, 57/330) and RV (8%, 25/330). The detection rate in the hospital setting was 27%, 15% and 14% for NV, SV and RV respectively, whereas in the community setting the detection rate of RV was < 1%. Among each of the investigated viruses one particular genogroup or genotype was dominant; GII.4 (82%) for NV, GI (46%) for SV and G1P[8] (64%) in RV. These variants were also found in higher proportions in the hospital setting compared to the community setting. The GII.4.2006 Minerva strain circulating globally since 2006 was the most common among genotyped NV in this study, with the GII.4-2010 New Orleans emerging in 2010.

Conclusions

This study shows that NV has become the leading viral cause of gastroenteritis at hospital and community settings in Nicaragua after implementation of RV vaccination.

Diagnosis of viral gastroenteritis in children: interpretation of real-time PCR results and relation to clinical symptoms

Molecular methods such as real-time polymerase chain reaction (PCR) are rapidly replacing traditional tests to detect fecal viral pathogens in childhood diarrhea. This technique has now increased the analytical sensitivity so drastically that positive results are found in asymptomatic children, leading to complex interpretation of real-time PCR results and difficult distinction between asymptomatic shedding and etiological cause of disease. We performed a review of the literature including pediatric studies using real-time PCR and a minimal inclusion period of one year to exclude bias by seasonality. We searched for studies on rotavirus, norovirus, adenovirus, astrovirus, and sapovirus, known to be the most common viruses to cause gastroenteritis in the pediatric population. For these viruses, we summarized the detection rates in hospitalized and community-based children with clinical symptoms of gastroenteritis, as well as subjects with asymptomatic viral shedding. Moreover, insight is given into the different viral sero- and genotypes causing pediatric gastroenteritis. We also discuss the scoring systems for severity of disease and their clinical value. A few published proposals have been made to improve the clinical interpretation of real-time PCR results, which we recapitulate and discuss in this review. We propose using the semi-quantitative measure of real-time PCR, as a surrogate for viral load, in relation to the severity score to distinguish asymptomatic viral shedding from clinically relevant disease. Overall, this review provides a better understanding of the scope of childhood gastroenteritis, discusses a method to enhance the interpretation of real-time PCR results, and proposes conditions for future research to enhance clinical implementation.

Management strategies in the treatment of neonatal and pediatric gastroenteritis

Acute gastroenteritis, characterized by the onset of diarrhea with or without vomiting, continues to be a major cause of morbidity and mortality in children in mostly resource-constrained nations. Although generally a mild and self-limiting disease, gastroenteritis is one of the most common causes of hospitalization and is associated with a substantial disease burden. Worldwide, up to 40% of children aged less than 5 years with diarrhea are hospitalized with rotavirus. Also, some microorganisms have been found predominantly in resource-constrained nations, including Shigella spp, Vibrio cholerae, and the protozoan infections. Prevention remains essential, and the rotavirus vaccines have demonstrated good safety and efficacy profiles in large clinical trials. Because dehydration is the major complication associated with gastroenteritis, appropriate fluid management (oral or intravenous) is an effective and safe strategy for rehydration. Continuation of breastfeeding is strongly recommended. New treatments such as antiemetics (ondansetron), some antidiarrheal agents (racecadotril), and chemotherapeutic agents are often proposed, but not yet universally recommended. Probiotics, also known as "food supplement," seem to improve intestinal microbial balance, reducing the duration and the severity of acute infectious diarrhea. The European Society for Paediatric Gastroenterology, Hepatology and Nutrition and the European Society of Paediatric Infectious Diseases guidelines make a stronger recommendation for the use of probiotics for the management of acute gastroenteritis, particularly those with documented efficacy such as Lactobacillus rhamnosus GG, Lactobacillus reuteri, and Saccharomyces boulardii. To date, the management of acute gastroenteritis has been based on the option of "doing the least": oral rehydration-solution administration, early refeeding, no testing, no unnecessary drugs.

Development and application of a SYBR green RT-PCR for first line screening and quantification of porcine sapovirus infection

BACKGROUND

Sapoviruses are single stranded positive sense RNA viruses belonging to the family Caliciviridae. The virus is detected in different species including the human and the porcine species as an enteric pathogen causing asymptomatic to symptomatic enteritis. In this study, we report the development of a rapid real time qRT-PCR based on SYBR Green chemistry for the diagnosis of porcine sapovirus infection in swine.

RESULTS

The method allows the detection of porcine sapoviruses and the quantification of the genomic copies present in stool samples. During its development, the diagnostic tool showed good correlation compared with the gold standard conventional RT-PCR and was ten-fold more sensitive. When the method was applied to field samples, porcine noroviruses from genogroup 2 genotype 11b were also detected. The method was also applied to swine samples from the Netherlands that were positive for PoSaV infection. Phylogenetic results obtained from the samples showed that PoSaV sequences were genetically related to the currently described genogroup III, to the proposed genogroup VII and also to the MI-QW19 sequence (close to the human SaV sequences).

CONCLUSIONS

A rapid, sensitive, and reliable diagnosis method was developed for porcine sapovirus diagnosis. It correlated with the gold standard conventional RT-PCR. Specificity was good apart for genogroup 2 genotype 11b porcine noroviruses. As a first line screening diagnosis method, it allows a quicker and easier decision on doubtful samples.

Norovirus infection in pediatric hematopoietic stem cell transplantation recipients: incidence, risk factors, and outcome

Norovirus infections are increasingly being recognized as important causes of diarrhea in hematopoietic stem cell transplantation (HSCT) recipients. This retrospective study aimed to evaluate the cumulative incidence, risk factors, and outcomes of norovirus infection in pediatric HSCT recipients. Among 55 patients age <21 years who underwent first HSCT between July 2007 and June 2011, 49 patients developed diarrhea and had stool tested for norovirus. Eight of these patients were found to be infected with norovirus. All were sporadic cases and manifested with nausea, vomiting, and diarrhea. The median age of these patients was 5.2 years (range, 0.5-18.5 years). Six were males. Seven patients underwent unrelated donor HSCT, and 1 patient underwent autologous cord blood HSCT. Two patients had norovirus infection before HSCT that persisted after transplantation. In the remaining 6 patients, norovirus developed at a median of 36.5 days posttransplantation (range, 5-517 days). The cumulative incidence of norovirus infection was 12.9% at 2 years posttransplantation. Risk factors for norovirus infection included the use of peripheral blood or cord blood as the stem cell source (P = .043) and administration of fludarabine (P = .002) and alemtuzumab (P = .011). The median time to viral clearance was 145 days (range, 13-263 days). Four-year survival was similar in norovirus-infected patients and noninfected patients (56.3% versus 58.3%).

False positive of an immunochromatography kit for detection of norovirus in neonatal feces

Norovirus was detected in the feces from five neonates in the growing care unit by a rapid immunochromatography (ICG) kit. However, confirmation using reverse transcription polymerase chain reaction (RT-PCR), RT-loop-mediated isothermal amplification (RT-LAMP), and nested RT-PCR methods showed negative results from all the feces. In addition, the ICG test for the detection of norovirus was positive for four cases out of the 16 feces from other asymptomatic neonates/infants. Only one feces out of the four samples was positive by RT-LAMP. In this study, among the factors related to false positives with the norovirus ICG kit, there were no differences regarding the commencement of feeding, nutrition, and sample collection methods. Since the false positive rate of ICG in the diagnosis of norovirus infection in neonates and early infancy is high, ICG is not an appropriate method, and it is necessary to confirm the results using reliable methods like RT-PCR.

Prevalence of norovirus GII-4 antibodies in Finnish children

Noroviruses (NoVs) are the second most common cause of viral gastroenteritis after rotavirus in children. NoV genotype GII-4 has emerged as the major type not only in outbreaks of NoV gastroenteritis but also endemic gastroenteritis among infants and young children worldwide. Using baculovirus-insect cell system virus-like particles (VLPs) of NoV genotype GII-4 and an uncommon genotype GII-12 were produced. These VLPs were used in enzyme-linked immunosorbent assays (ELISA) for detection of NoV-specific immunoglobulin G (IgG) and IgA antibodies in 492 serum specimens from Finnish children 0-14 years of age collected between 2006 and 2008. NoV IgG antibody prevalence was 47.3% in the age group 7-23 months and increased up to 91.2% after the age of 5 years. Avidity of NoV IgG antibodies was low in the primary infections while high avidity antibodies were detected in the recurrent infections of the older children. In GII-4 infections, the homologous antibody response to GII-4 VLPs was stronger than to GII-12 VLPs but cross-reactivity between GII-4 and GII-12 was observed. Binding of GII-4 VLPs to a putative carbohydrate antigen receptor H-type 3 could be blocked by sera from children not infected with NoV during a waterborne outbreak of acute gastroenteritis. Therefore, protection against NoV infection correlated with strong blocking activity.

Impact of norovirus/sapovirus-related diarrhea in renal transplant recipients hospitalized for diarrhea

BACKGROUND

Diarrhea of unspecified cause frequently occurs after renal transplantation and is usually ascribed to mycophenolic acid toxicity. Norovirus (NoV) and sapovirus (SaV) have been sporadically reported to cause chronic diarrhea in immunocompromised patients.

METHODS

We undertook a retrospective study (2008-2009) to examine the clinical and epidemiologic significance of NoV and SaV infections in adult renal transplant recipients hospitalized for acute or chronic diarrhea.

RESULTS

Ninety-six renal transplant recipients were hospitalized for diarrhea at our institution during a 16-month period, 87 of whom were included in the study, including 46 patients with chronic diarrhea. Among 41 patients with unexplained diarrhea, 20 patients were screened for NoV/SaV, 16 of whom were positive. Fifteen of them (94%) had chronic diarrhea. When compared with bacterial and parasitic infections, NoV/SaV infections were associated with a greater weight loss at the time of admission, a 8.7-fold longer duration of symptoms and a more frequent need for mycophenolic acid dosage reduction. Eighty-one percent of patients hospitalized for NoV/SaV-associated diarrhea experienced acute renal failure. Five and one patients subsequently had biopsy-diagnosed active graft rejection and oxalate nephropathy, respectively. Ten of the 14 patients who underwent a longitudinal study of NoV/SaV stool's clearance exhibited a prolonged viral shedding period with a median time of 289 days (107-581 days).

CONCLUSIONS

Our study indicates that NoV/SaV infection causes posttransplant chronic diarrhea potentially complicated by severe kidney graft impairment.

Norovirus: a possible cause of pneumatosis intestinalis

OBJECTIVE

Pneumatosis intestinalis (PI) in children is associated with immunosuppression, mucosal disruption from trauma, obstructive pulmonary disease, congenital heart disease, and gastrointestinal infections. Our study is the first report of norovirus infection-associated PI.

PATIENTS AND METHODS

A retrospective review was performed in pediatric patients (older than 30 days) with PI from March 2005 to April 2009. Since December 2008, in addition to routine stool examinations, reverse-transcriptase polymerase chain reaction testing for calicivirus (norovirus and sapovirus), adenovirus, astrovirus, and enterovirus has been performed.

RESULTS

Twenty-seven patients with PI were identified. The median age was 1.4 (range 0.2-14.8 years). Seventeen patients (63.0%) were immunocompromised hosts. Pathogens were identified in 5 immunocompromised patients (5/27 and 5/8 since December 2008). Of note, norovirus was identified in 4 patients (80%, 4/5) during the cold weather season. The genotype of noroviruses in these patients was GII-4. Among 27 patients with PI, 10 patients (37.0%) developed PI in the spring and 11 (40.7%) in the winter. Twenty-four patients survived (88.9%, 24/27). None of the patients with norovirus or rotavirus infection died.

CONCLUSIONS

Our data suggest that norovirus infection may contribute to the development of PI in immunocompromised hosts.

Prevention and treatment of viral diarrhea in pediatrics

Diarrhea is the second largest cause of mortality worldwide in children from the perinatal period to the age of 5 years. Rotavirus has been the most commonly identified viral cause of diarrhea in children. Norovirus is now recognized as the second most common viral pathogen. Adenovirus, astrovirus and sapovirus are the other major viral causes of pediatric gastroenteritis. Strategies for prevention include basic hygiene, optimization of nutrition and, ultimately, vaccination. Two new vaccines have recently been licensed for the prevention of rotavirus, the monovalent human rotavirus vaccine (Rotarix) and the pentavalent bovine-human reassortant vaccine (RotaTeq). These vaccines have already dramatically decreased the morbidity associated with rotavirus in countries where they are widely used. Efforts to develop a norovirus vaccine face substantial hurdles. Treatment of the viral pathogens is primarily limited to symptomatic measures.

Tracking environmental norovirus contamination in a pediatric primary immunodeficiency unit

Norovirus strains were detected in two patients and in environmental swabs from a pediatric primary immunodeficiency unit in London, United Kingdom, during an infection control incident in November and December 2007. Detailed analyses of the gene encoding the P2 domain demonstrated that the majority of the strains were not related to the patients and that the environmental contamination was most likely due to secondary transfer by the hands of staff or visitors.

Endocytosis of murine norovirus 1 into murine macrophages is dependent on dynamin II and cholesterol

Although noroviruses cause the vast majority of nonbacterial gastroenteritis in humans, little is known about their life cycle, including viral entry. Murine norovirus (MNV) is the only norovirus to date that efficiently infects cells in culture. To elucidate the productive route of infection for MNV-1 into murine macrophages, we used a neutral red (NR) infectious center assay and pharmacological inhibitors in combination with dominant-negative (DN) and small interfering RNA (siRNA) constructs to show that clathrin- and caveolin-mediated endocytosis did not play a role in entry. In addition, we showed that phagocytosis or macropinocytosis, flotillin-1, and GRAF1 are not required for the major route of MNV-1 uptake. However, MNV-1 genome release occurred within 1 h, and endocytosis was significantly inhibited by the cholesterol-sequestering drugs nystatin and methyl-beta-cyclodextrin, the dynamin-specific inhibitor dynasore, and the dominant-negative dynamin II mutant K44A. Therefore, we conclude that the productive route of MNV-1 entry into murine macrophages is rapid and requires host cholesterol and dynamin II.

High-resolution x-ray structure and functional analysis of the murine norovirus 1 capsid protein protruding domain

Murine noroviruses (MNV) are closely related to the human noroviruses (HuNoV), which cause the majority of nonbacterial gastroenteritis. Unlike HuNoV, MNV grow in culture and in a small-animal model that represents a tractable model to study norovirus biology. To begin a detailed investigation of molecular events that occur during norovirus binding to cells, the crystallographic structure of the murine norovirus 1 (MNV-1) capsid protein protruding (P) domain has been determined. Crystallization of the bacterially expressed protein yielded two different crystal forms (Protein Data Bank identifiers [PDB ID], 3LQ6 and 3LQE). Comparison of the structures indicated a large degree of structural mobility in loops on the surface of the P2 subdomain. Specifically, the A'-B' and E'-F' loops were found in open and closed conformations. These regions of high mobility include the known escape mutation site for the neutralizing antibody A6.2 and an attenuation mutation site, which arose after serial passaging in culture and led to a loss in lethality in STAT1(-/-) mice, respectively. Modeling of a Fab fragment and crystal structures of the P dimer into the cryoelectron microscopy three-dimensional (3D) image reconstruction of the A6.2/MNV-1 complex indicated that the closed conformation is most likely bound to the Fab fragment and that the antibody contact is localized to the A'-B' and E'-F' loops. Therefore, we hypothesize that these loop regions and the flexibility of the P domains play important roles during MNV-1 binding to the cell surface.

Mixed viral infections causing acute gastroenteritis in children in a waterborne outbreak

We examined stool specimens for viral pathogens from 50 children referred to hospital due to acute gastroenteritis (AGE) resulting from consuming drinking water contaminated with sewage in a Finnish community using PCR methods. Rotavirus was detected in 33 (66%), human calicivirus in 31 (62%), and both in 40% of cases. Of the caliciviruses, 20/31 (65%) were noroviruses and 11 (35%) sapoviruses. Furthermore, Aichi virus was detected in 25 (50%), adenovirus in six (12%) and bocavirus in four (8%) cases. Campylobacter jejuni was present in 20 (61%) and Salmonella in four (12%) of the 33 stools cultured for bacteria. On a 20-point scale median severity score of AGE in the 28 hospitalized children was 17; the severity was similar regardless of viruses detected. Bloody diarrhoea occurred only when C. jejuni was present. To conclude, massive exposure to several AGE viruses caused mixed infections and severe AGE regardless of the aetiological agents.

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.

Ganglioside-linked terminal sialic acid moieties on murine macrophages function as attachment receptors for murine noroviruses

Noroviruses are the major cause of nonbacterial gastroenteritis in humans. However, little is known regarding the norovirus life cycle, including cell binding and entry. In contrast to human noroviruses, the recently discovered murine norovirus 1 (MNV-1) readily infects murine macrophages and dendritic cells in culture. Many viruses, including the related feline calicivirus, use terminal sialic acids (SA) as receptors for infection. Therefore, we tested whether SA moieties play a role during MNV-1 infection of murine macrophages. Competition with SA-binding lectins and neuraminidase treatment led to a reduction in MNV-1 binding and infection in cultured and primary murine macrophages, suggesting a role for SA during the initial steps of the MNV-1 life cycle. Because SA moieties can be attached to glycolipids (i.e., gangliosides), we next determined whether MNV-1 uses gangliosides during infection. The gangliosides GD1a, GM1, and asialo-GM1 (GA1) are natural components of murine macrophages. MNV-1 bound to ganglioside GD1a, which is characterized by an SA on the terminal galactose, but not to GM1 or asialo-GM1 in an enzyme-linked immunosorbent assay. The depletion of gangliosides using an inhibitor of glycosylceramide synthase (d-threo-P4) led to a reduction of MNV-1 binding and infection in cultured and primary murine macrophages. This defect was specifically rescued by the addition of GD1a. A similar phenotype was observed for MNV field strains WU11 (GV/WU11/2005/USA) and S99 (GV/Berlin/2006/DE). In conclusion, our data indicate that MNV can use terminal SA on gangliosides as attachment receptors during binding to murine macrophages.

Abnormal computed tomography findings among children with viral gastroenteritis and symptoms mimicking acute appendicitis

OBJECTIVE

To evaluate computed tomography (CT) findings in pediatric patients with viral gastroenteritis who presented with clinical features of acute abdomen.

PATIENTS AND METHODS

During 2 seasons of viral gastroenteritis from 2005 to 2007, 302 children with acute gastrointestinal symptoms were admitted to our center for treatment of dehydration and associated complications. Stool specimens obtained from 130 of the 302 were tested for norovirus with the reverse transcriptase-polymerase chain reaction method.

RESULTS

Among the 130 patients, 44 tested positive for norovirus, 34 for rotavirus, and 1 for adenovirus. In the remaining 51, except one with Campylobacter jejuni, no viral or bacterial pathogen was detectable. An abdominal CT scan was performed in 4 patients with norovirus and in 1 with rotavirus for suspected acute abdomen including acute appendicitis. Computed tomography (CT) findings were similar among the 5 patients, including thickening of the bowel wall and fluid-filled bowel loops in the small intestine with no pathological findings in the stomach, appendix, or colon.

CONCLUSIONS

Anatomical changes in the small intestine were shown by CT in 5 children with viral gastroenteritis who presented with acute abdomen. These imaging features of viral gastroenteritis may be useful in differential diagnosis of acute abdomen to avoid unnecessary surgery.

Contamination of the hospital environment with gastroenteric viruses: comparison of two pediatric wards over a winter season

The aims of this study were to examine the extent of gastroenteric virus contamination in a pediatric primary immunodeficiency (PPI) ward and a general pediatric ward over a winter season and to determine whether changes to hospital infection control interventions would have an impact on environmental contamination levels within pediatric units. Environmental swabs were collected weekly from 11 sites in both wards from 15 December 2005 to 3 March 2006 and examined for the presence of norovirus (NoV), astrovirus, and rotavirus (RV) by reverse transcriptase PCR. Viruses were detected in 17% and 19% of swabs from both wards. Virus contamination for NoV and RV decreased from 20% to 6% and 15% to 10% of swabs, respectively, in the PPI ward from the 2004 study by Gallimore et al. (C. I. Gallimore, C. Taylor, A. R. Gennery, A. J. Cant, A. Galloway, M. Iturriza-Gomara, and J. J. Gray, J. Clin. Microbiol. 44:395-399, 2006). Overall, changes to cleaning protocols were deemed to have reduced the level of environmental contamination with gastroenteric viruses, but contamination still occurred due to a breakdown in infection control procedures indicated by contamination in areas frequented by parents but used only occasionally by staff.

Pediatric norovirus diarrhea in Nicaragua

Information about norovirus (NoV) infections in Central America is limited. Through a passive community and hospital pediatric diarrhea surveillance program, a total of 542 stool samples were collected between March 2005 and February 2006 in León, Nicaragua. NoV was detected in 12% (65/542) of the children; of these, 11% (45/409) were in the community and 15% (20/133) were in the hospital, with most strains (88%) belonging to genogroup II. NoV infections were age and gender associated, with children of <2 years of age (P < 0.05) and girls (P < 0.05) being most affected. Breast-feeding did not reduce the number of NoV infections. An important proportion (57%) of NoV-infected children were coinfected with diarrheagenic Escherichia coli. A significant proportion (18/31) of NoV-positive children with dehydration required intravenous rehydration. Nucleotide sequence analysis (38/65) of the N-terminal and shell region in the capsid gene revealed that at least six genotypes (GI.4, GII.2, GII.4, GII.7, GII.17, and a potentially novel cluster termed "GII.18-Nica") circulated during the study period, with GII.4 virus being predominant (26/38). The majority (20/26) of those GII.4 strains shared high nucleotide homology (99%) with the globally emerging Hunter strain. The mean viral load was approximately 15-fold higher in children infected with GII.4 virus than in those infected with other G.II viruses, with the highest viral load observed for the group of children infected with GII.4 and requiring intravenous rehydration. This study, the first of its type from a Central American country, suggests that NoV is an important etiological agent of acute diarrhea among children of <2 years of age in Nicaragua.

Detection of viral agents of gastroenteritis: Norovirus, Sapovirus and Astrovirus

Norovirus, Sapovirus and Astrovirus are causative agents of viral gastroenteritis affecting all age groups, but most frequently the young, the elderly and persons in semi-closed communities such as hospitals, nursing homes, military bases and cruise ships. The sensitive and rapid detection of causative agents of viral gastroenteritis is key to the effective implementation of infection control systems. Traditional detection methods such as electron microscopy and antigen detection assays lack sensitivity. The detection of gastrointestinal viruses by molecular methods has resulted in increased levels of detection, and enables the epidemiological investigation of viral strains. The significant diversity of gastrointestinal viruses, in particular Norovirus and Sapovirus, are compounded by increasing reports of virus recombination, and pose an ongoing challenge to the development of sensitive and specific molecular detection assays.

Human caliciviruses in symptomatic and asymptomatic infections in children in Vellore, South India

Pediatric gastroenteritis is a major cause of childhood morbidity and mortality worldwide, especially in developing countries. It has been increasingly recognised that human caliciviruses (HuCV), comprising noroviruses (NoV), and sapoviruses (SaV), are important in both outbreak and non-outbreak settings. This study aimed to characterise caliciviruses detected in the faeces of hospitalized children and children in the community in India. This study examined 350 faecal samples from children presenting to the hospital with acute gastroenteritis and 673 samples collected from children in the community, 500 from children with diarrhea, and 173 samples from children without diarrhea. Strain characterisation was performed by reverse transcription-polymerase chain reaction (RT-PCR) and partial sequencing of the gene encoding the RNA-dependent RNA polymerase (RdRp) and/or a region spanning the open reading frames (ORFs) 1 and 2 (ORF1/ORF2) junction. A total of 68 of 350 specimens (19.4%) from hospitalized children were positive, and SaV and NoV accounted for 5.1 and 15.1% of the infections, respectively. Mixed infections of HuCVs with other enteric pathogens were seen in 9.4% of the total children tested. Sixty-eight out of 673 (10.1%) samples collected from children in the community were positive for caliciviruses, and SaV and NoV accounted for 3.4 and 6.6% of the infections. In the community cohort 55/500 (11%) and 13/173 (7.5%) were from symptomatic and asymptomatic children, respectively, and SaVs accounted for 17/500 (3.4%) and NoVs for 38/500 (7.6%) of the symptomatic infections. This is the first report of genotyping of circulating caliciviruses in both hospital and community in India and has increased the evidence for the role of these viruses in pediatric gastroenteritis in India.

Norovirus-associated encephalopathy

Norovirus is a common cause of gastroenteritis. We describe the case of a 23-month-old girl with encephalopathy possibly associated with norovirus infection. The viral genome was detected in stool, serum and cerebrospinal fluid (CSF) by reverse transcription polymerase chain reaction. This is the first report of encephalopathy potentially caused by norovirus as indicated by the presence of the virus genome in CSF.

Norovirus outbreak in a pediatric oncology unit

OBJECTIVE

Norovirus (NV) is an etiologic agent of outstanding importance that can cause severe epidemic gastroenteritis in day-care centers, schools, nursing homes, and hospitals. Therefore NV requires foremost attention as a pathogen responsible for epidemics of gastroenteritis in immunocompromised inpatients. In this study, a NV outbreak in a pediatric oncology unit is described and the consequences for this high-risk population are discussed.

MATERIAL AND METHODS

Stool and vomitus samples from 11 patients were tested for NV and other relevant viruses during the outbreak by reverse transcriptase-polymerase chain reaction (RT-PCR) and/or enzyme-linked immunosorbent assay (ELISA) (whenever an appropriate ELISA was available). Norwalk virus PCR amplifications were sequenced and phylogenetic analysis was performed.

RESULTS

The index patient and the chain of infection were identified. Follow-up investigation surprisingly demonstrated viral shedding for a maximum of 140 days (median 23 days). Three patients experienced severe or life-threatening symptoms, probably related to NV infection.

CONCLUSIONS

In the event of an outbreak of gastroenteritis (involving two or more symptomatic patients) in a pediatric oncology unit, the search for NV in stool or vomitus specimens should be initiated in good time. As long as the data are limited regarding whether a detectable viral antigen or RNA in stools represents an infectious virus, patients have to be isolated as long as the diagnostic assays remain positive. During the acute phase of the illness, health-care workers should wear masks in addition to practicing meticulous hand hygiene with a disinfectant of proven activity against NV. Pediatric oncology patients must be closely monitored during follow-up investigations as they may shed the virus for months. There is some evidence from the outbreak described here that those patients face a greater risk of severe NV-related complications.

Acute diarrheal disease in children: epidemiology, prevention, and treatment

Diarrhea is one of the most common causes of morbidity and mortality in children worldwide. The causes of acute diarrhea in children vary with the location, time of year, and population studied. There is increasing recognition of a widening array of enteric pathogens associated with diarrheal diseases. Adequate fluid and electrolyte replacement and maintenance are key to managing diarrheal illnesses. Thorough clinical and epidemiologic evaluation is needed to define the severity and type of illness, exposures, and whether the patient in is immunocompromised to direct the performance of selective diagnosis cultures, toxin testing, parasite studies, and the administration of antimicrobial therapy.