Can Use of Viral Load Improve Norovirus Clinical Diagnosis and Disease Attribution?

Diagnosing viral gastro-enteritis using the fully automated sample-in, result-out STARlet All in one system (AIOS)

The STARlet All-In-One system is a modular platform that integrates the complete molecular diagnostic workflow from nucleic acid extraction of clinical samples to PCR set-up and amplification. The platform was evaluated in comparison with laboratory developed tests (LDT) on fecal samples from patients with suspected viral gastro-enteritis. In a retrospective study, 72 positive samples were analysed, including all pathogens detected by the Seegene Allplex™ GI-virus assay, adenovirus, astrovirus, norovirus GI and GII, sapovirus, and rotavirus. Concordant results were obtained for 69 samples (96 %). Three discordant results were observed, one norovirus GII positive that gave an invalid result in the AIOS and two samples that were negative in the AIOS. One adenovirus positive that was subtyped as a genotype 2 virus, which is not associated with gastro-enteritis, and a sapovirus. In the prospective part of the study, 661 fecal samples were included. A total of 61 positive samples were detected, of which 60 were also detected by the AIOS. One norovirus GII positive sample (CT 35.2) was tested negative in the AIOS. Two additional sapovirus positive samples, CT 37 and 38, were detected by the AIOS but not by the LDT. The STARlet All-In-One platforms results in an automated molecular workflow with reduced hands-on time and enables running assays during out of office hours. Application of the Seegene Allplex™ GI-virus assay showed excellent concordance to the current diagnostic LDT. In a prospective comparison, only three discordant results were observed, all with CT values over 35 and therefore unlikely of clinical relevance.

Asymptomatic norovirus infection during outbreaks in China: A systematic review and meta-analysis

Acute gastroenteritis outbreaks may be caused by the excretion of norovirus (NoV) from asymptomatic individuals. Despite numerous studies involving asymptomatic NoV infection during outbreaks in China, a comprehensive assessment of its role has not been conducted, which is critical for emergency management. Our objective was to assess the prevalence of asymptomatic NoV infection during outbreaks in China. We conducted a comprehensive search of multiple databases, including PubMed, Web of Science, Cochrane Library, China National Knowledge Infrastructure, China Wanfang, and China Weipu, between January 1, 1997 and June 19, 2023. The retrieved articles and their references underwent screening, which utilized polymerase chain reaction-based assays for the detection of NoV in asymptomatic individuals during outbreaks that occurred in China. The primary summary data were the prevalence of asymptomatic NoV infection in outbreaks. We generated pooled estimates of asymptomatic prevalence in the population as a whole and in subgroups by using random-effect models. Of the 97 articles included, the pooled asymptomatic prevalence of NoV among 5117 individuals in outbreaks was 17.6% (95% confidence interval [CI]: 14.1-21.3). The asymptomatic prevalence of NoV GII (17.1%, 95% CI: 12.9-21.5) was similar to that of NoV GI (22.0%, 95% CI: 12.8-32.4). However, the proportion of asymptomatic individuals involved in NoV GII (57.44%) was significantly higher than that of NoV GI (5.12%), and NoV GII (75.26%) was reported much more frequently than NoV GI (14.43%) in the included articles. Meta-regression analysis of 11 possible influencing factors (geographic region, setting, season, sample type, genotype, transmission route, occupation, age, per capita income, study quality, and cases definition) showed that the source of heterogeneity might be related to the outbreak settings, per capita income, and study quality (p = 0.037, 0.058, and 0.026, respectively). Of particular note was the asymptomatic prevalence peaked in preschoolers (27.8%), afterward, it fell into trough in elementary and junior school children (10.5%), before the second peak located in adults (17.8%), and the elderly (25.2%). Prevalent genotypes reported include GII.4, followed by GII.17, GII.2, GII.3, GII.6, and so forth. The estimated asymptomatic prevalence of NoV during outbreaks in China was as high as 17.6%, with NoV GII dominating. In addition, genetic subtypes of NoV in outbreaks should be detected whenever possible. The role of asymptomatic individuals in NoV outbreaks cannot be ignored. This knowledge will help governments develop public health policies and emergency response strategies for outbreaks, assess the burden, and develop vaccines.

Norovirus Epidemiology and Genotype Circulation during the COVID-19 Pandemic in Brazil, 2019-2022

Norovirus stands out as a leading cause of acute gastroenteritis (AGE) worldwide, affecting all age groups. In the present study, we investigated fecal samples from medically attended AGE patients received from nine Brazilian states, from 2019 to 2022, including the COVID-19 pandemic period. Norovirus GI and GII were detected and quantified using RT-qPCR, and norovirus-positive samples underwent genotyping through sequencing the ORF1/2 junction region. During the four-year period, norovirus prevalence was 37.2%, varying from 20.1% in 2020 to 55.4% in 2021. GII genotypes dominated, being detected in 92.9% of samples. GII-infected patients had significantly higher viral concentrations compared to GI-infected patients (median of 3.8 × 107 GC/g and 6.7 × 105 GC/g, respectively); and patients aged >12-24 months showed a higher median viral load (8 × 107 GC/g) compared to other age groups. Norovirus sequencing revealed 20 genotypes by phylogenetic analysis of RdRp and VP1 partial regions. GII.4 Sydney[P16] was the dominant genotype (57.3%), especially in 2019 and 2021, followed by GII.2[P16] (14.8%) and GII.6[P7] (6.3%). The intergenogroup recombinant genotype, GIX.1[GII.P15], was detected in five samples. Our study is the first to explore norovirus epidemiology and genotype distribution in Brazil during COVID-19, and contributes to understanding the epidemiological dynamics of norovirus and highlighting the importance of continuing to follow norovirus surveillance programs in Brazil.

Chimeric virus-like particles of human norovirus constructed by structure-guided epitope grafting elicit cross-reactive immunity against both GI.1 and GII.4 genotypes

IMPORTANCE

Human norovirus (HuNoV) is highly infectious and can result in severe illnesses in the elderly and children. So far, there is no effective antiviral drug to treat HuNoV infection, and thus, the development of HuNoV vaccines is urgent. However, NoV evolves rapidly, and currently, at least 10 genogroups with numerous genotypes have been found. The genetic diversity of NoV and the lack of cross-protection between different genotypes pose challenges to the development of broadly protective vaccines. In this study, guided by structural alignment between GI.1 and GII.4 HuNoV VP1 proteins, several chimeric-type virus-like particles (VLPs) were designed through surface-exposed loop grafting. Mouse immunization studies show that two of the designed chimeric VLPs induced cross-immunity against both GI.1 and GII.4 HuNoVs. To our knowledge, this is the first designed chimeric VLPs that can induce cross-immune activities across different genogroups of HuNoV, which provides valuable strategies for the development of cross-reactive HuNoV vaccines.

Global prevalence of asymptomatic norovirus infection in outbreaks: a systematic review and meta-analysis

BACKGROUND

Although many studies on asymptomatic norovirus infection in outbreaks have been conducted globally, structured data (important for emergency management of outbreaks) on the prevalence of this epidemic are still not available. This study assessed the global prevalence of asymptomatic norovirus infection in outbreaks.

METHODS

We identified publications on asymptomatic infections from norovirus outbreaks by searching the PubMed, Embase, Cochrane Library, Medline, and Web of Science databases and screening references from the articles reviewed. Prevalence of asymptomatic norovirus infection in outbreaks was employed as the primary summary data. The random-effects model of the meta-analysis was fitted to generate estimates of the prevalence in the overall and subgroup populations.

RESULTS

In total, 44 articles with a sample size of 8,115 asymptomatic individuals were included. The estimated pooled prevalence of asymptomatic norovirus infection in outbreaks was 21.8% (95%CI, 17.4-27.3). The asymptomatic prevalence of norovirus GII (20.1%) was similar to that of GI (19.8%); however, the proportion prevalence of asymptomatic individuals involved in the former (33.36%) was significantly higher than that of in the latter (0.92%) and the former (93.18%) was reported much more frequently than the latter (15.91%) in the included articles. These studies had significant heterogeneity (I2 = 92%, τ2 = 0.4021, P < 0.01). However, the source of heterogeneity could not be identified even after subgroup analysis of 10 possible influencing factors (geographical area, outbreak settings, outbreak seasons, sample types, norovirus genotypes, transmission routes, subjects' occupations, subjects' age, per capita national income, and clear case definition). Meta-regression analysis of these 10 factors demonstrated that the geographical area could be partly responsible for this heterogeneity (P = 0.012).

CONCLUSIONS

The overall pooled asymptomatic prevalence of norovirus in outbreaks was high, with genome II dominating. Asymptomatic individuals may play an important role in norovirus outbreaks. This knowledge could help in developing control strategies and public health policies for norovirus outbreaks.

Age-associated features of norovirus infection analysed in mice

Norovirus (NoV) is the leading global cause of viral gastroenteritis. Young children bear the highest burden of disease and play a key role in viral transmission throughout the population. However, which host factors contribute to age-associated variability in NoV severity and shedding are not well-defined. The murine NoV (MNoV) strain CR6 causes persistent infection in adult mice and targets intestinal tuft cells. Here we find that natural transmission of CR6 from infected dams occurred only in juvenile mice. Direct oral CR6 inoculation of wild-type neonatal mice led to accumulation of viral RNA in the ileum and prolonged shedding in the stool that was replication-independent. This viral exposure induced both innate and adaptive immune responses including interferon-stimulated gene expression and MNoV-specific antibody responses. Interestingly, viral uptake depended on passive ileal absorption of luminal virus, a process blocked by cortisone acetate administration, which prevented ileal viral RNA accumulation. Neonates lacking interferon signalling in haematopoietic cells were susceptible to productive infection, viral dissemination and lethality, which depended on the canonical MNoV receptor CD300LF. Together, our findings reveal developmentally associated aspects of persistent MNoV infection, including distinct tissue and cellular tropism, mechanisms of interferon regulation and severity of infection in the absence of interferon signalling. These emphasize the importance of defining viral pathogenesis phenotypes across the developmental spectrum and highlight passive viral uptake as an important contributor to enteric infections in early life.

Asymptomatic Norovirus Infection Among Children in Kindergartens and Primary Schools - Beijing Municipality, China, 2021

What is already known about this topic?

Children in kindergartens and primary schools are the high-incidence groups of norovirus acute gastroenteritis. However, asymptomatic norovirus infection among them is seldom reported.

What is added by this report?

The norovirus positive rate was 3.48% among asymptomatic children in kindergartens and primary schools in Beijing Municipality in June 2021, the most common genotype was GII.4 Sydney, and no acute gastroenteritis outbreak was reported over the study period.

What are the implications for public health practice?

The asymptomatic norovirus infection was relatively low among kindergarten children and primary school students in summer. Norovirus genotypes in asymptomatic children were similar to those circulating in the symptomatic cases. Asymptomatic norovirus infection may play a limited role in causing acute gastroenteritis outbreaks.

Role of Noroviruses in Sporadic Acute Gastroenteritis Cases from Children Attending a Large Referral Children's Hospital in Buenos Aires City, Argentina

BACKGROUND

Noroviruses (NVs) are recognized as the leading cause of sporadic and epidemic acute gastroenteritis worldwide, in all age groups. Although there is increasing knowledge that NVs are responsible for many acute gastroenteritis outbreaks in Argentina, studies to estimate prevalence in sporadic cases are scarce.

METHODS

A descriptive, observational and cross-sectional study was conducted with children under 5 years with acute gastroenteritis attending the outpatient department at the "Ricardo Gutiérrez" Children's Hospital (RGCH) in Buenos Aires City between June 2017 and June 2021. Sociodemographic, clinical and epidemiologic data were recorded. Stool samples were tested and genotyped for norovirus. Association between norovirus detection and demographic and clinical variables was assessed.

RESULTS

A total of 350 children with acute diarrhea were included, of which stool samples were collected for 332 (94.9%). Norovirus was detected in 81 cases (24.4%). Vomiting and moderate/severe diarrhea were more frequent in norovirus-positive than norovirus-negative children. However, the presence of watery diarrhea and a history of rotavirus vaccination were significantly associated with norovirus etiology. GII and GII.4 were the most frequently detected genogroup and genotype, respectively.

CONCLUSIONS

NVs were detected with high frequency, mostly in children between 6 months and 2 years old, reinforcing the hypothesis of a newly updated scenario of norovirus predominance over rotavirus. Watery diarrhea, complete vaccination against rotavirus and vomiting are 3 key parameters that should raise suspicion of possible norovirus gastroenteritis. Continuous and active norovirus surveillance in this age group is important because children represent a priority group for norovirus vaccine design and development.

Epidemiology of GII.4 and GII.2 norovirus outbreaks in closed and semi-closed institutions in 2017 and 2018

Norovirus infections are a leading cause of acute gastroenteritis outbreaks worldwide, with genotypes GII.2 and GII.4 being the most prevalent. The aim of this study was to compare the characteristics of GII.2 and GII.4 norovirus outbreaks reported in Catalonia in closed or semi-closed institutions in 2017 and 2018. The epidemiological and clinical characteristics of GII.2 and GII.4 outbreaks were compared using the chi-square test or Fisher's exact test for categorical variables and the Mann-Whitney U test for continuous variables. Odds ratios and their 95% confidence intervals were estimated. 61 outbreaks were reported: GII.4 was the causative agent in 12 outbreaks (30%) and GII.2 in 9 outbreaks (22.5%). GII.2 outbreaks were detected more frequently in schools or summer camps (66.7%) and GII.4 outbreaks in nursing homes (91.7%) (p = 0.01). Ninety-three people were affected in GII.2 outbreaks and 94 in GII.4 outbreaks. The median age was 15 years (range: 1-95 years) in GII.2 outbreaks and 86 years (range: 0-100 years) in GII.4 outbreaks (p < 0.001). Nausea, abdominal pain, and headache were observed more frequently in persons affected by GII.2 outbreaks (p < 0.05). Symptomatic cases presented a higher viral load suggestive of greater transmission capacity, although asymptomatic patients presented relevant loads indicative of transmission capacity.

Norovirus outbreaks in long-term care facilities in Catalonia from 2017 to 2018

Norovirus is the leading cause of outbreaks of acute viral gastroenteritis. We carried out this study to investigate outbreaks in long-term care facilities reported in 2017 and 2018 in Catalonia (Spain). The characteristics of the centers, exposed persons and the genogroups responsible were analyzed. Viral loads were estimated. The attack rate (AR) of the outbreaks studied, and the rate ratio (RR) and the odds ratio (OR) and their 95% confidence intervals as measures of association were calculated. The mean cycle thresholds were compared using the t-test for independent means. We included 30 outbreaks (4631 exposed people). The global AR was 25.93%. The RR of residents vs. staff was 2.28 (95% CI 2.0–2.6). The RR between AR in residents with total or severe dependence vs. residents with moderate, low or no-dependence was 1.23 (95% CI 1.05–1.45). The AR were higher in smaller centers than in larger ones (38.47% vs. 19.25% and RR 2; 95% CI 1.82–2.2). GII was responsible for 70% of outbreaks. No association was found between the genogroup and presenting symptoms (OR 0.96; 95% CI 0.41–2.26). Viral loads were higher in symptomatic than in asymptomatic patients (p = 0.001).

Characteristics of GII.4 Norovirus Versus Other Genotypes in Sporadic Pediatric Infections in Davidson County, Tennessee, USA

BACKGROUND

Norovirus is a leading cause of epidemic acute gastroenteritis (AGE), with most outbreaks occurring during winter. The majority of outbreaks are caused by GII.4 noroviruses; however, data to support whether this is true for sporadic medically attended AGE are limited. Therefore, we sought to compare the clinical characteristics and seasonality of GII.4 vs non-GII.4 viruses.

METHODS

Children aged 15 days -17 years with AGE symptoms were recruited from the outpatient, emergency department, and inpatient settings at Vanderbilt Children's Hospital, Davidson County, Nashville, Tennessee, from December 2012 -November 2015. Stool specimens were tested using qRT-PCR for GI and GII noroviruses and subsequently genotyped by sequencing a partial region of the capsid gene.

RESULTS

A total of 3705 patients were enrolled, and stool specimens were collected and tested from 2885 (78%) enrollees. Overall, 636 (22%) samples were norovirus-positive, of which 567 (89%) were GII. Of the 460 (81%) genotyped GII-positive samples, 233 (51%) were typed as GII.4 and 227 (49%) as non-GII.4. Compared with children with non-GII.4 infections, children with GII.4 infections were younger, more likely to have diarrhea, and more likely to receive oral rehydration fluids. Norovirus was detected year-round and peaked during winter.

CONCLUSIONS

Approximately 40% of sporadic pediatric norovirus AGE cases were caused by GII.4 norovirus. Children infected with GII.4 had more severe symptoms that required more medical care. Seasonal variations were noticed among different genotypes. These data highlight the importance of continuous norovirus surveillance and provide important information on which strains pediatric norovirus vaccines should protect against.

Virological and Epidemiological Features of Norovirus Infections in Brazil, 2017-2018

Noroviruses are considered an important cause of acute gastroenteritis (AGE) across all age groups. Here, we investigated the incidence of norovirus, genotypes circulation, and norovirus shedding in AGE stool samples from outpatients in Brazil. During a two-year period, 1546 AGE stool samples from ten Brazilian states were analyzed by RT-qPCR to detect and quantify GI and GII noroviruses. Positive samples were genotyped by dual sequencing using the ORF1/2 junction region. Overall, we detected norovirus in 32.1% of samples, with a massive predominance of GII viruses (89.1%). We also observed a significant difference between the median viral load of norovirus GI (3.4×10⁵ GC/g of stool) and GII (1.9×10⁷ GC/g). The most affected age group was children aged between 6 and 24 m old, and norovirus infection was detected throughout the year without marked seasonality. Phylogenetic analysis of partial RdRp and VP1 regions identified six and 11 genotype combinations of GI and GII, respectively. GII.4 Sydney[P16] was by far the predominant genotype (47.6%), followed by GII.2[P16], GII.4 Sydney[P31], and GII.6[P7]. We detected, for the first time in Brazil, the intergenogroup recombinant genotype GIX.1[GII.P15]. Our study contributes to the knowledge of norovirus genotypes circulation at the national level, reinforcing the importance of molecular surveillance programs for future vaccine designs.

Factors associated with the detection of norovirus among asymptomatic adults

OBJECTIVES

Little is known about asymptomatic norovirus infection and its risk factors in healthy adults. This study investigated detection of norovirus in stool and its associated factors among asymptomatic healthy adults in a high-income country.

METHODS

This prospective cross-sectional study-conducted between February 2016 and January 2017 at a teaching hospital in Japan-included apparently healthy adults aged ≥18 years who underwent voluntary health check-ups. Our primary outcome was detection of norovirus in stool specimens confirmed by real-time RT-PCR. We evaluated descriptive statistics and associated factors, including demographics, social habits, and clinical parameters.

RESULTS

Among 15 532 participants, 4536 (29.2%, mean age 58.0 (standard deviation 11.8) years, male 44.6%) were enrolled, and 112 (2.5%, GI 57, GII 54, GI + GII 1) were norovirus-positive. Monthly prevalence rates of the GI norovirus were consistent throughout the year, while those of GII were high in May. Participants aged <40 and ≥ 80 years had higher rates of GII norovirus detection. Participants who occasionally consume alcohol, especially wine (odds ratio (OR) 0.17, 95% confidence interval (CI) 0.04-0.68), had lower norovirus detection rates than abstainers. Participants with untreated dyslipidaemia and a low high-density lipoprotein (HDL) cholesterol level had higher detection rates than those with treated dyslipidaemia (OR 1.48, 95%CI 1.07-2.05) and a normal HDL cholesterol level (OR 2.60, 95%CI 1.46-4.61). Some gastrointestinal and female genital diseases were associated with norovirus detection.

CONCLUSIONS

The norovirus detection rate in asymptomatic adults was 2.5%. Participants with specific lifestyles or medical histories may have higher risks of asymptomatic norovirus infection.

Evaluation of PCR cycle threshold values by patient population with the quidel lyra SARS-CoV-2 assay

The Lyra SARS-CoV-2 assay was the primary method for molecular testing performed at Barnes-Jewish Healthcare System in St. Louis, Missouri during the initial COVID-19 surge from mid-March to late-April 2020. We performed a retrospective analysis of 1,043 positive Lyra SARS-CoV-2 results during these 36 days to investigate associations between cycle threshold (C_T)  value and patient characteristics. Total RNA were extracted from NP or OP swabs using either the EasyMag or KingFisher automated extraction systems and quantified with RotorGene Q (Qiagen) or Applied Biosystems 7500 Fast Dx thermocyclers respectively. Notably, we found lower a significant median lower C_T for samples tested on the KingFisher-ABI 7500 fastDX (KF/ABI) system compared to the EasyMag/RotorGene (EM/RGQ) platform. Since 77.5% of our tests were ran on the EM/RGQ pipeline we then perform additional analysis on these values and found that C _T values in outpatient care settings compared to samples obtained in the emergency department or inpatient had significantly lower C _T values. These collective findings suggests a difference in viral load amongst various patient populations.

The Changing Landscape of Pediatric Viral Enteropathogens in the Post-Rotavirus Vaccine Era

BACKGROUND

Acute gastroenteritis (AGE) is a common reason for children to receive medical care. However, the viral etiology of AGE illness is not well described in the post-rotavirus vaccine era, particularly in the outpatient (OP) setting.

METHODS

Between 2012 and 2015, children 15 days through 17 years old presenting to Vanderbilt Children's Hospital, Nashville, Tennessee, with AGE were enrolled prospectively from the inpatient, emergency department, and OP settings, and stool specimens were collected. Healthy controls (HCs) were enrolled and frequency matched for period, age group, race, and ethnicity. Stool specimens were tested by means of reverse-transcription real-time quantitative polymerase chain reaction for norovirus, sapovirus, and astrovirus RNA and by Rotaclone enzyme immunoassay for rotavirus antigen, followed by polymerase chain reaction verification of antigen detection.

RESULTS

A total of 3705 AGE case patients and 1563 HCs were enrolled, among whom 2885 case patients (78%) and 1110 HCs (71%) provided stool specimens that were tested. All 4 viruses were more frequently detected in AGE case patients than in HCs (norovirus, 22% vs 8%, respectively; rotavirus, 10% vs 1%; sapovirus, 10% vs 5%; and astrovirus, 5% vs 2%; P < .001 for each virus). In the OP setting, rates of AGE due to norovirus were higher than rate for the other 3 viruses. Children <5 years old had higher OP AGE rates than older children for all viruses.

CONCLUSIONS

Norovirus remains the most common virus detected in all settings, occurring nearly twice as frequently as the next most common pathogens, sapovirus and rotavirus. Combined, norovirus, sapovirus, rotavirus, and astrovirus were associated with almost half of all AGE visits and therefore are an important reason for children to receive medical care.

Associations Between Relative Viral Load at Diagnosis and Influenza A Symptoms and Recovery

BACKGROUND

Rapid point-of-care polymerase chain reaction (PCR) diagnostic tests generally provide a qualitative result of positive or negative only. Additional information about the relative viral load could be calculated. Such quantitative information might be useful for making treatment decisions.

METHODS

We enrolled students at a university health center who presented with cough and 1 additional flu-like symptom from December 2016 to February 2017. Data were collected before, during, and 5 days after the clinic visit. All those enrolled in the study received a point-of-care PCR test (cobas Liat). For those patients that tested positive for influenza A, we investigated correlations between the relative viral load and measures of disease severity and recovery.

RESULTS

One hundred thirty-five students tested positive for influenza A. We found a positive correlation between viral load and body temperature. Time since symptom onset seemed to have a negative correlation but was not statistically significant. We did not find any correlations between viral load and overall symptom severity or outcomes related to recovery.

CONCLUSIONS

Although we found a correlation between relative viral load and body temperature, for our study population of young, overall healthy adults, we did not find that relative viral load provided additional information that could help in determining treatment and disease outcomes. It could be that viral load does provide useful additional information for other groups of patients, such as young children or older adults. Further studies on those populations are warranted.

Birth Cohort Studies Assessing Norovirus Infection and Immunity in Young Children: A Review

Globally, noroviruses are among the foremost causes of acute diarrheal disease, yet there are many unanswered questions on norovirus immunity, particularly following natural infection in young children during the first 2 years of life when the disease burden is highest. We conducted a literature review on birth cohort studies assessing norovirus infections in children from birth to early childhood. Data on infection, immunity, and risk factors are summarized from 10 community-based birth cohort studies conducted in low- and middle-income countries. Up to 90% of children experienced atleast one norovirus infection and up to 70% experienced norovirus-associated diarrhea, most often affecting children 6 months of age and older. Data from these studies help to fill critical knowledge gaps for vaccine development, yet study design and methodological differences limit comparison between studies, particularly for immunity and risk factors for disease. Considerations for conducting future birth cohort studies on norovirus are discussed.

Use of Human Intestinal Enteroids to Detect Human Norovirus Infectivity

Tools to detect human norovirus infectivity have been lacking. Using human intestinal enteroid cultures inoculated with GII.Pe-GII.4 Sydney–infected fecal samples, we determined that a real-time reverse transcription PCR cycle threshold cutoff of 30 may indicate infectious norovirus. This finding could be used to help guide infection control.

Higher Viral Load of Emerging Norovirus GII.P16-GII.2 than Pandemic GII.4 and Epidemic GII.17, Hong Kong, China

We compared viral load of emerging recombinant norovirus GII.P16-GII.2 with those for pandemic GII.Pe-GII.4 and epidemic GII.P17-GII.17 genotypes among inpatients in Hong Kong. Viral load of GII.P16-GII.2 was higher than those for other genotypes in different age groups. GII.P16-GII.2 is as replication competent as the pandemic genotype, explaining its high transmissibility and widespread circulation.

Performance evaluation of a newly developed molecular assay for the accurate diagnosis of gastroenteritis associated with norovirus of genogroup II

The performance of a newly proposed fully automated cassette-based sample-to-results solution for norovirus (NoV) detection, InGenius Norovirus ELITe MGB®, was evaluated. A total of 120 selected archival stool samples from children hospitalized for acute gastroenteritis were used to compare the results to a reference real-time RT-PCR. The InGenius NoV assay showed optimal diagnostic accuracy (sensitivity, 100%; specificity, 95.7%) and was able to correctly detect the entire wide panel of epidemiologically relevant genotypes tested. These preliminary results suggest that the InGenius NoV assay can be recommended as a valuable method for accurate diagnosis of NoV GII infection in epidemic and sporadic gastroenteritis.

Sensitive Genotyping of Foodborne-Associated Human Noroviruses and Hepatitis A Virus Using an Array-Based Platform

Human noroviruses (NoV) are the leading cause of human gastroenteritis in populations of all ages and are linked to most of the foodborne outbreaks worldwide. Hepatitis A virus (HAV) is another important foodborne enteric virus and is considered the most common agent causing acute liver disease worldwide. In the present study, a focused, low-density DNA microarray was developed and validated for the simultaneous identification of foodborne-associated genotypes of NoV and HAV. By employing a novel algorithm, capture probes were designed to target variable genomic regions commonly used for typing these foodborne viruses. Validation results showed that probe signals, specific for the tested NoV or HAV genotypes, were on average 200-times or 38-times higher than those detected for non-targeted genotypes, respectively. To improve the analytical sensitivity of this method, a 12-mer oligonucleotide spacer sequence was added to the capture probes and resulted in a detection threshold of less than 10 cRNA transcripts. These findings have indicated that this array-based typing sensor has the accuracy and sensitivity for identifying NoV and HAV genotypic profiles predominantly linked to food poisoning. The implementation of this typing sensor would thus provide highly relevant and valuable information for use in surveillance and outbreak attribution.