Fecal Viral Load and Norovirus-associated Gastroenteritis

Chan, Martin C.W.; Sung, Joseph J.Y.; Lam, Robert F.; Chan, Paul K.S.; Lee, Nelson; Lai, Robin Kit-Ho; Leung, Wai K.

doi:10.3201/eid1208.060081

Cited by 168 publications

(100 citation statements)

References 9 publications

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“…As for clinical samples, the concentrations of NoVs per gram of stool varied, ranging from 10 3 to 10 8 . These findings are consistent with published data indicating that in patients with NoV gastroenteritis, viral particles can reach 10 10 per gram faeces during the acute phase (Chan et al 2006). As demonstrated in 2006 by Chan and collaborators, viral concentrations in the faeces of patients infected with NoV GII are higher than in those infected with NoV GI (which could explain the former's higher transmissibility via the faecal-oral route).…”

Section: Discussionsupporting

confidence: 90%

Quantification of Norovirus Genogroups I and II in Environmental and Clinical Samples Using TaqMan Real-Time RT-PCR

et al. 2008

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Noroviruses (NoVs) are a major cause of acute non-bacterial gastroenteritis in all age groups. They efficiently circulate in both clinical and environmental contexts. In this study, real-time RT-PCR methods based on TaqMan probe technology were used to enumerate human noroviruses (genogroups I and II) in clinical samples, and in estuarine, seawater and sewage water samples, with the aim of obtaining quantitative information on the level of viral contamination. This was achieved through a quantitative analysis of the highly conserved region between ORF1 and ORF2, using genogroup-specific assays. RNA standards used to construct calibration curves for the two genogroups were generated by in vitro transcription from recombinant pCR4TOPO vectors containing a partial sequence coding for RdRp polymerase. Sewages were found to contain from 6.8 9 10 2 to 6.7 9 10 4 genome copies (GC) per millilitre; seawater samples contained from 7.6 9 10 1 to 2.4 9 10 3 per 10 l. As for clinical samples, the concentrations of NoVs per gram of stool varied, ranging from 6.1 9 10 3 to 1.4 9 10 8 . Real-time PCR is an easy to use, sensitive and specific tool able to generate quantitative data, and could prove useful in both environmental and clinical settings.

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Section: Discussionsupporting

confidence: 90%

Quantification of Norovirus Genogroups I and II in Environmental and Clinical Samples Using TaqMan Real-Time RT-PCR

et al. 2008

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“…We also observed a predominance (84%, n ϭ 64) of positive GII specimens in our study, a result which has been noted in a previous study where GII viruses accounted for ϳ62% of norovirus outbreaks (20). Control of norovirus outbreaks is complicated by the relatively low infectious dose (21) and by the high level of norovirus shedding in vomitus (21) and feces (22). Routine norovirus prevention and control measures utilize a combination of staff-and patientlevel strategies, including hand hygiene, assigning of patient cohorts, use of appropriate protective equipment, and effective environmental disinfection (23,24).…”

Section: Discussionsupporting

confidence: 86%

Multicenter Evaluation of the Xpert Norovirus Assay for Detection of Norovirus Genogroups I and II in Fecal Specimens

et al. 2016

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Norovirus is the most common cause of sporadic gastroenteritis and outbreaks worldwide. The rapid identification of norovirus has important implications for infection prevention measures and may reduce the need for additional diagnostic testing. The Xpert Norovirus assay recently received FDA clearance for the detection and differentiation of norovirus genogroups I and II (GI and GII), which account for the vast majority of infections. In this study, we evaluated the performance of the Xpert Norovirus assay with both fresh, prospectively collected (n ‫؍‬ 914) and frozen, archived (n ‫؍‬ 489) fecal specimens. A Centers for Disease Control and Prevention (CDC) composite reference method was used as the gold standard for comparison. For both prospective and frozen specimens, the Xpert Norovirus assay showed positive percent agreement (PPA) and negative percent agreement (NPA) values of 98.3% and 98.1% for GI and of 99.4% and 98.2% for GII, respectively. Norovirus prevalence in the prospective specimens (collected from March to May of 2014) was 9.9% (n ‫؍‬ 90), with the majority of positives caused by genogroup II (82%, n ‫؍‬ 74). The positive predictive value (PPV) of the Xpert Norovirus assay was 75% for GI-positive specimens, whereas it was 86.5% for GII-positive specimens. The negative predictive values (NPV) for GI and GII were 100% and 99.9%, respectively. G lobally, norovirus is the most common cause of endemic and epidemic gastroenteritis in all age groups (1). Within the United States, it is estimated that norovirus infections account for 400,000 emergency room visits, 56,000 to 71,000 hospitalizations, and 570 to 800 deaths annually (2). In countries that have implemented rotavirus vaccination programs, norovirus has become the leading cause of gastroenteritis in young children, in both outpatient and hospitalized individuals (3-6).Norovirus, originally called Norwalk virus, was identified from a gastroenteritis outbreak in Norwalk, OH, when the viral particles were visualized using electron microscopy (7). Genomic sequence data place norovirus in the genus Norovirus in the family Caliciviridae, which also includes Sapovirus, Lagovirus, Nebovirus, and Vesivirus, which are all small, nonenveloped, positive-sense RNA viruses. Currently, there are 7 known genogroups of norovirus, designated genogroup I (GI) to GVII, and over 40 genotypes (8). The majority of norovirus infections in humans are caused by GI and GII viruses (9). Norovirus can be transmitted via the fecaloral route, through aerosolization of viral particles in vomitus (10, 11), and through contaminated food, water, and environmental sources (12).Norovirus infections are characterized by a variety of symptoms, including vomiting, nonbloody diarrhea, abdominal pain, nausea, and a low-grade fever. In otherwise healthy individuals, norovirus infections are typically self-limiting and resolve within a few days of symptom onset. However, norovirus symptoms can be more severe and prolonged in the elderly, young children, and immunocompromised individual...

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“…In addition to the high analytical sensitivity, RT-qPCR assays can also be used to determine the amount of nucleic acid in a sample in a semiquantitative way as a proxy to determine the viral load. Patients with higher viral loads have been reported to excrete the virus longer, and data from several studies suggest that GII viruses (i.e., GII.4) are shed in larger amounts than GI viruses (30).…”

Section: Diagnostic Methodsmentioning

confidence: 99%

Advances in Laboratory Methods for Detection and Typing of Norovirus

2015

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Human noroviruses are the leading cause of epidemic and sporadic gastroenteritis across all age groups. Although the disease is usually self-limiting, in the United States norovirus gastroenteritis causes an estimated 56,000 to 71,000 hospitalizations and 570 to 800 deaths each year. This minireview describes the latest data on laboratory methods (molecular, immunological) for norovirus detection, including real-time reverse transcription-quantitative PCR (RT-qPCR) and commercially available immunological assays as well as the latest FDA-cleared multi-gastrointestinal-pathogen platforms. In addition, an overview is provided on the latest nomenclature and molecular epidemiology of human noroviruses.

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Fecal Viral Load and Norovirus-associated Gastroenteritis

Cited by 168 publications

References 9 publications

Quantification of Norovirus Genogroups I and II in Environmental and Clinical Samples Using TaqMan Real-Time RT-PCR

Quantification of Norovirus Genogroups I and II in Environmental and Clinical Samples Using TaqMan Real-Time RT-PCR

Multicenter Evaluation of the Xpert Norovirus Assay for Detection of Norovirus Genogroups I and II in Fecal Specimens

Advances in Laboratory Methods for Detection and Typing of Norovirus

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