Common Cause Of Epidemic Gastroenteritis Research Articles

Environmental Surveillance of Genogroup I and II Noroviruses in Shandong Province, China in 2013.

Noroviruses are the most common cause of epidemic gastroenteritis. However, the case-based surveillance is limited in China. In this study, we analyzed the results of environmental surveillance conducted in two cities of Shandong Province, China from January to December in 2013. Twenty-four sewage samples were collected and concentrated via membrane absorption/elution method. After reverse transcription-PCR, cloning and sequencing on ORF2 region, norovirus nucleic acid was detected in all 24 sewage samples. A total of 403 norovirus sequences of 16 genotypes were detected, among which GII.3 (22.6%), GI.2 (17.1%), GI.5 (13.4%), GI.3 (11.9%), GII.4 (7.7%), and GII.6 (6.7%) were the 6 most common genotypes. Phylogenetic analysis revealed multiple lineages within most common genotypes, especially in GI.3, whereas all GII.4 sequences belonged to Sydney 2012 strain. Recombination events were observed in 5 GI and 4 GII sequences within or near the ORF1/ORF2 overlap. This is the first report on systematic environmental surveillance on norovirus in China. The data presented here reveal co-circulation and high genetic diversity of multiple norovirus genotypes in the two cities, and suggest continued environmental surveillance can provide valuable information on norovirus circulation in the population.

Environmental Transmission of Human Noroviruses in Shellfish Waters

Human noroviruses (NoV) are the most common cause of epidemic gastroenteritis following consumption of bivalve shellfish contaminated with fecal matter. NoV levels can be effectively reduced by some sewage treatment processes such as activated sludge and membrane bioreactors. However, tertiary sewage treatment and substantial sewage dilution are usually required to achieve low concentrations of virus in shellfish. Most outbreaks have been associated with shellfish harvested from waters affected by untreated sewage from, for example, storm overflows or overboard disposal of feces from boats. In coastal waters, NoV can remain in suspension or associate with organic and inorganic matter and be accumulated by shellfish. Shellfish take considerably longer to purge NoV than fecal indicator bacteria when transferred from sewage-polluted estuarine waters to uncontaminated waters. The abundance and distribution of NoV in shellfish waters are influenced by the levels of sewage treatment, proximity of shellfish beds to sewage sources, rainfall, river flows, salinity, and water temperature. Detailed site-specific information on these factors is required to design measures to control the viral risk.

Seroepidemiology of Norovirus‐Associated Travelers' Diarrhea

Noroviruses (NoVs) are the most common cause of epidemic gastroenteritis, responsible for at least 50% of all gastroenteritis outbreaks worldwide and were recently identified as a leading cause of travelers' diarrhea (TD) in US and European travelers to Mexico, Guatemala, and India. Serum and diarrheic stool samples were collected from 75 US student travelers to Cuernavaca, Mexico, who developed TD. NoV RNA was detected in acute diarrheic stool samples using reverse transcription-polymerase chain reaction (RT-PCR). Serology assays were performed using GI.1 Norwalk virus (NV) and GII.4 Houston virus (HOV) virus-like particles (VLPs) to measure serum levels of immunoglobulin A (IgA) and IgG by dissociation-enhanced lanthanide fluorescent immunoassay (DELFIA); serum IgM was measured by capture enzyme-linked immunosorbent assay (ELISA), and the 50% antibody-blocking titer (BT50 ) was determined by a carbohydrate-blocking assay. NoV infection was identified in 12 (16%; 9 GI-NoV and 3 GII-NoV) of 75 travelers by either RT-PCR or fourfold or more rise in antibody titer. Significantly more individuals had detectable preexisting IgA antibodies against HOV (62/75, 83%) than against NV (49/75, 65%) (p = 0.025) VLPs. A significant difference was observed between NV- and HOV-specific preexisting IgA antibody levels (p = 0.0037), IgG (p = 0.003), and BT50 (p = <0.0001). None of the NoV-infected TD travelers had BT50 > 200, a level that has been described previously as a possible correlate of protection. We found that GI-NoVs are commonly associated with TD cases identified in US adults traveling to Mexico, and seroprevalence rates and geometric mean antibody levels to a GI-NoV were lower than to a GII-NoV strain.

Norovirus Outbreak in Iran

Implication for health policy/practice/research/medical education: Norovirus is the most common cause of epidemic gastroenteritis, responsible for at least 50% of all gastroenteritis outbreaks worldwide, and a major cause of foodborne illnesses. Due to the recent outbreak of norovirus in the northern area of Tehran, this report reviews the recent advances and provides guidelines for outbreak management and disease prevention for medical practitioners Copyright © 2013, Shahid Beheshti University of Medical Sciencces;. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Due to the recent outbreak of norovirus in the northern area of Tehran, this report reviews the recent advances and provides guidelines for outbreak management and disease prevention for medical practitioners. Norovirus is the most common cause of epidemic gastroenteritis, responsible for at least 50% of all gastroenteritis outbreaks worldwide, and a major cause of foodborne illnesses. In the United States, approximately 21 million illnesses attributable to norovirus are estimated to occur annually. Since 2001, when the most recent norovirus recommendations were published (1), substantial advances have been made in norovirus epidemiology, immunology, diagnostic methods, and infection control. As molecular diagnostic techniques have improved and become more widely available, detection and reporting of norovirus outbreaks have increased. Although the inability to culture human noroviruses in vitro has hampered the progression, assessment of the performance of disinfectants has been facilitated by the discovery of new, cultivable surrogates for human noroviruses. In addition, the periodic emergences of epidemic strains (from genogroup II type 4, GII.4) as well as outbreaks in specific populations (e.g. the elderly in nursing homes) have been characterized (1). The prototype norovirus was first identified as the cause of a gastroenteritis outbreak in Norwalk, Ohio, in 1968 (2). However, the epidemiology of noroviruses remained poorly characterized until relatively recently, because of the lack of widespread availability of sensitive diagnostic methods (3). Noroviruses are a group of nonenveloped, single-stranded RNA viruses, classified into the genus norovirus (previously referred to as Norwalk-like viruses (NLVs) or small round-structured viruses (SRSVs) of the caliciviridae family) (4). Noroviruses cause acute gastroenteritis in all ages. The illness typically begins after an incubation period of 12 48 hours and is characterized by acute onset, nonbloody diarrhea, vomiting, nausea, and abdominal cramps. Some patients might only experience vomiting or diarrhea. Low-grade fever and body aches might also be associated with the infection, and thus, the term stomach flu is often used to describe the illness, although there is no biological association with influenza. Although symptoms might be severe, they typically resolve without treatment after 1 3 days in otherwise healthy persons. However, more prolonged courses of illness lasting 4 6 days can occur, particularly among young children, elderly persons, and hospitalized patients (5, 6). Approximately 10% of cases with norovirus gastroenteritis seek medical attention, which might include hospitalization and treatment for dehydration with oral or intravenous fluid therapy. Norovirus-associated deaths have been reported among elderly and in the context of outbreaks in long-term-care facilities (7). Necrotizing enterocolitis in neonates, chronic diarrhea in immunosuppressed patients and post-infectious irritable bowel syndrome have also been reported in association with norovirus infections (8). Norovirus is extremely contagious, with an estimated infectious dose as low as 18 viral particles, suggesting that approximately 5 billion infectious doses might be contained in each gram of feces during peak shedding. Humans are the only known reservoirs for human norovirus infections and transmission occurs by three general routes: person-toperson, foodborne and waterborne. Person-to-person transmission might occur directly through the fecaloral route, by ingestion of aerosolized vomitus, or by indirect exposure to fomites or contaminated environmental surfaces. Foodborne transmission typically occurs via contamination by infected food handlers durAr ch ive f S ID

Severe Outcomes Are Associated With Genogroup 2 Genotype 4 Norovirus Outbreaks: A Systematic Literature Review

Noroviruses (NoVs) are the most common cause of epidemic gastroenteritis; however, the relative impacts of individual factors underlying severe illness are poorly understood. This report reviews published NoV outbreak reports to quantify hospitalization and mortality rates and assess their relationship with outbreak setting, transmission route, and strain. Using a string of terms related to "norovirus" and "outbreak," we 2435 nonduplicate articles identified in PubMed, EMBASE, and Web of Knowledge published between January 1993 and June 2011. Inclusion criteria included outbreaks with a minimum of 2 ill persons with a common exposure and at least 1 reverse-transcription polymerase chain reaction-confirmed case of NoV disease. Univariate analyses were performed, and multivariable models were fitted to estimate the independent effect of each factor. We analyzed 843 NoV outbreaks reported in 233 published articles from 45 countries. Based upon 71724 illnesses, 501 hospitalizations, and 45 deaths, overall hospitalization and mortality rates were 0.54% and 0.06%, respectively. In multivariate analysis, genogroup 2 genotype 4 (GII.4) NoV strains were associated with higher hospitalization (incidence rate ratio [IRR], 9.4; 95% confidence interval [CI], 6.1-14.4; P< .001) and mortality rates (IRR, 3.1; 95% CI, 1.3-7.6; P = .01). Deaths were much more likely to occur in outbreaks occurring in healthcare facilities (IRR, 60; 95% CI, 6-109; P = .01). Our review suggests that hospitalizations and deaths were more likely in outbreaks associated with GII.4 viruses, independent of other factors, and underscores the importance of developing vaccines against GII.4 viruses to prevent severe disease outcomes.

Comparative Evolution of GII.3 and GII.4 Norovirus over a 31-Year Period

Noroviruses are the most common cause of epidemic gastroenteritis. Genotype II.3 is one of the most frequently detected noroviruses associated with sporadic infections. We studied the evolution of the major capsid gene from seven archival GII.3 noroviruses collected during a cross-sectional study at the Children's Hospital in Washington, DC, from 1975 through 1991, together with capsid sequence from 56 strains available in GenBank. Evolutionary analysis concluded that GII.3 viruses evolved at a rate of 4.16 × 10(-3) nucleotide substitutions/site/year (strict clock), which is similar to that described for the more prevalent GII.4 noroviruses. The analysis of the amino acid changes over the 31-year period found that GII.3 viruses evolve at a relatively steady state, maintaining 4% distance, and have a tendency to revert back to previously used residues while preserving the same carbohydrate binding profile. In contrast, GII.4 viruses demonstrate increasing rates of distance over time because of the continued integration of new amino acids and changing HBGA binding patterns. In GII.3 strains, seven sites acting under positive selection were predicted to be surface-exposed residues in the P2 domain, in contrast to GII.4 positively selected sites located primarily in the shell domain. Our study suggests that GII.3 noroviruses caused disease as early as 1975 and that they evolve via a specific pattern, responding to selective pressures induced by the host rather than presenting a nucleotide evolution rate lower than that of GII.4 noroviruses, as previously proposed. Understanding the evolutionary dynamics of prevalent noroviruses is relevant to the development of effective prevention and control strategies.

Evaluation of the NucliSens® Basic Kit assay for detection of Norwalk virus RNA in stool specimens

Norwalk-like viruses (NLVs) are a genetically diverse group of human caliciviruses that are the most common cause of epidemic gastroenteritis and are detected typically in stool by reverse transcription (RT)-PCR or electron microscopy (EM). The application of a rapid nucleic acid sequence-based amplification (NASBA) assay for the detection of NLV RNA in stool is described using the NucliSens® Basic Kit. Primers and probes for the NLV Basic Kit assay were based on the RNA polymerase region of the prototype NLV, Norwalk virus (NV) genome and could consistently detect 10 4 RT-PCR detectable units of NV RNA in a stool filtrate. When compared directly with RT-PCR on a dilution series of NV stool filtrate, the NucliSens® Basic Kit assay was equally sensitive. Cross-reactivity studies with a representative panel of other enteric pathogens were negative. When applied to 15 stool specimens from NV-challenged volunteers, the NASBA Basic Kit application for NV detection yielded 100% sensitivity, 50% specificity, and 67% concordance, using RT-PCR as the ‘gold standard’. Despite the specificity of the NASBA primer/probe sequences for NV, other representatives from both NLV genogroups I and II could be detected by the Basic Kit assay in outbreak stool specimens, although the results were inconsistent. Our results suggest that the NucliSens® Basic Kit assay provides a rapid and sensitive alternative to RT-PCR for detecting NV RNA in stool specimens. However, improvements in test specificity and primer design will be needed before the assay can be used routinely in the clinical setting.

Genomic diversity of "Norwalk like viruses" (NLVs): pediatric infections in a Brazilian shantytown.

"Norwalk-like viruses" (NLVs) are a common cause of epidemic gastroenteritis in adults and children in developed countries. However, little is known about the role of NLVs in endemic pediatric gastroenteritis in developing countries. We sequenced Genogroup I and II NLV reverse transcription-polymerase chain reaction (RT-PCR) products from an 81-nucleotide region of the viral RNA polymerase gene to examine the molecular epidemiology of NLV infection in children younger than 5 years of age in Forteleza, Ceará, Brazil. NLV-positive PCR products were obtained from stool specimens collected over a 16-month period (1990-1991) from diarrhea cases and controls in a cohort of 120 children in an urban shantytown and from a study in the same city of hospitalized children with persistent diarrhea. Eight unique strains were detected in 15 specimens from 10 cohort children and in two hospital specimens. Nucleotide identity between the strains (5 Genogroup I, 3 Genogroup II) ranged from 63% to 88%. We designated these strains BraV1-8, for Brazil virus 1-8. The degree of genomic diversity of NLV strains we identified in this cohort during a short time period suggests multiple foci of infection within the community. Furthermore, sequence analysis of strains from two children with multiple symptomatic NLV infections indicates that infection with one strain was not protective against subsequent infection with a different strain in the same genogroup. These findings have implications for vaccine development and the prevention of pediatric gastroenteritis in developing countries.