Global prevalence of norovirus in cases of acute gastroenteritis from 1997 to 2021: An updated systematic review and meta-analysis

Epidemiology of viral gastroenteritis in children and genetic diversity of rotavirus strains in Kolkata, West Bengal after introduction of rotavirus vaccine

BACKGROUND

Despite global rotavirus vaccination efforts, rotavirus remains a leading cause of childhood deaths from acute gastroenteritis. Post-vaccination studies in India, particularly in eastern India, have been limited, despite high prevalence of rotavirus in this region prior to vaccine introduction. This study was conducted to assess the impact of rotavirus vaccine on the epidemiology of rotavirus and other enteric viruses, as well as the changes in the diversity of rotavirus strains among children (≤5 years) with acute gastroenteritis.

METHODS

A total of 877 stool samples from children hospitalized with acute diarrhea during 2022-2023, were screened for enteric viruses using multiplex PCR. Rotavirus positive samples were genotyped by sequencing and phylogenetic analysis of VP4 and VP7 genes were done.

RESULTS AND DISCUSSION

Out of 877 diarrheal cases, 47 % tested positive for at least one enteropathogenic virus. Rotavirus was most prevalent (25.9 %), followed by norovirus (11.4 %), adenovirus-F (10.6 %), and astrovirus (5.3 %). Among mixed infections, rotavirus and norovirus co-infections were the most common. Rotavirus infection was highest in children aged 12-24 months, while other enteric viruses were more common in the 6-24 month age group. Clinical severity was higher among rotavirus-infected patients compared to those infected with other enteric viruses. The G3P[8] genotype of rotavirus predominated, with notable increase in G2P[4] and the detection of rare strains like G3P[6] and G11P[25]. G3P[6] was identified for the first time in this region showing Wa-like genome constellation. Unlike pre-vaccine period, G9 genotype was not detected. Mutations in antigenic epitope of circulating strains compared to vaccine strains may affect vaccine efficacy.

CONCLUSION

The study highlights the persistent burden of childhood diarrhea despite rotavirus vaccination. Subtle alterations in the proportion of other enteric viruses and diversity of circulating rotavirus genotypes in the post-vaccination period were observed. Continuous long-term surveillance is required to evaluate the impact of vaccine in this region.

Sensitivity-enhanced hydrogel digital RT-LAMP with in situ enrichment and interfacial reaction for norovirus quantification in food and water

Low levels of human norovirus (HuNoV) in food and environment present challenges for nucleic acid detection. This study reported an evaporation-enhanced hydrogel digital reverse transcription loop-mediated isothermal amplification (HD RT-LAMP) with interfacial enzymatic reaction for sensitive HuNoV quantification in food and water. By drying samples on a chamber array chip, HuNoV particles were enriched in situ. The interfacial amplification of nucleic acid at the hydrogel-chip interface was triggered after coating HD RT-LAMP system. Nanoconfined spaces in hydrogels provided a simple and rapid "digital format" to quantify single virus within 15 min. Through in situ evaporation for enrichment, the sensitivity level was increased by 20 times. The universality of the sensitivity-enhanced assay was also verified using other bacteria and virus. Furthermore, a deep learning model and smartphone app were developed for automatic amplicon analysis. Multiple actual samples, including 3 lake waters, strawberry, tap water and drinking water, were in situ enriched and detected for norovirus quantification using the chamber arrays. Therefore, the sensitivity-enhanced HD RT-LAMP is an efficient assay for testing biological hazards in food safety monitoring and environmental surveillance.

Utilizing Zebrafish Embryos for Replication of Tulane Virus: A Human Norovirus Surrogate

The zebrafish larvae/embryo model has been shown to support the replication of seven strains (G1.7[P7], GII.2[P16], GII.3[P16], GII.4[P4], GII.4[P16], GII.6[P7], and GII.17[P13]) of human norovirus (HuNoV). However, due to challenges in consistently obtaining HuNoV-positive stool samples from clinical sources, evaluating HuNoV surrogates in this model is highly valuable. This study assesses the potential of zebrafish embryos and larvae as a model for Tulane virus (TuV) replication. Three infection methods were examined: microinjection, immersion, and feeding. Droplet digital PCR was used to quantify viral RNA across all three infection methods. Microinjection of 3 nL of TuV into zebrafish embryos (< 6-h post-fertilization) resulted in significant replication, with viral RNA levels reaching 6.22 logs at 4-day post-infection. In contrast, the immersion method showed no replication after immersing 4-day post-fertilization (dpf) larvae in TuV suspension for 6 h. Similarly, no replication was observed with the feeding method, where Paramecium caudatum loaded with TuV were fed to 4 dpf larvae. The findings indicate that the zebrafish embryo model supports TuV replication through the microinjection method, suggesting that TuV may serve as a useful surrogate for studying HuNoV pathogenesis. Additionally, TuV can be utilized in place of HuNoV in method optimization studies using the zebrafish embryo model, circumventing the limited availability of HuNoV.

CRISPR/Cas13a analysis based on NASBA amplification for norovirus detection

Human norovirus (HuNoV) is a leading cause of foodborne diseases worldwide, making rapid and accurate detection crucial for prevention and control. In recent years, the CRISPR/Cas13a system, known for its single-base resolution in RNA recognition and unique collateral cleavage activity, is particularly suitable for sensitive and rapid RNA detection. However, isothermal amplification-based CRISPR/Cas13 assays often require an external transcription step, complicating the detection process. In our study, an efficient diagnostic technique based on the NASBA/Cas13a system was established to identify conserved regions at the ORF1-ORF2 junction of norovirus. The RNA amplification techniques [Nucleic Acid Sequence-Based Amplification (NASBA)] integrates reverse transcription and transcription steps, enabling sensitive, accurate, and rapid enrichment of low-abundance RNA. Furthermore, the CRISPR/Cas13a system provides secondary precise recognition of the amplified products, generating a fluorescence signal through its activated accessory collateral cleavage activity. We optimized the reaction kinetics parameters of Cas13a and achieved a detection limit as low as 51pM. The conditions for the cascade reaction involving CRISPR analysis and RNA amplification were optimized. Finally, we validated the reliability and accuracy of the NASBA/Cas13a method by detecting norovirus in shellfish, achieving results comparable to qRT-PCR in a shorter time and detecting viral loads as low as 10 copies/μL.

Leishmania tarentolae as a platform for the production of vaccines against viral pathogens

Infectious diseases remain a persistent public health problem and a leading cause of morbidity and mortality in both humans and animals. The most effective method of combating viral infections is the widespread use of prophylactic vaccinations, which are administered to both people at risk of disease and animals that may serve as significant sources of infection. Therefore, it is crucial to develop technologies for the production of vaccines that are highly effective, easy to transport and store, and cost-effective. The protein expression system based on the protozoan Leishmania tarentolae offers several advantages, validated by numerous studies, making it a good platform for producing vaccine antigens. This review provides a comprehensive overview into the potential applications of L. tarentolae for the safe production of effective viral antigens.

Norovirus acute gastroenteritis amongst US and European travellers to areas of moderate to high risk of travellers' diarrhoea: a prospective cohort study

BACKGROUND

Acute gastroenteritis (AGE) is a major medical condition for travellers worldwide, particularly travellers to low- and middle-income countries. Norovirus (NoV) is the most common cause of viral AGE in older children and adults, but data on prevalence and impact amongst travellers is limited.

METHODS

Prospective, multi-site, observational cohort study conducted 2015-2017, amongst adult international travellers from the US and Europe to areas of moderate to high risk of travel-acquired AGE. Participants provided self-collected pre-travel stool samples and self-reported AGE symptoms whilst travelling. Post-travel stool samples were requested from symptomatic subjects and a sample of asymptomatic travellers within 14 days of return. Samples were tested for NoV by RT-qPCR, genotyped if positive and tested for other common enteric pathogens by Luminex xTAG GPP.

RESULTS

Of the 1109 participants included, 437 (39.4%) developed AGE symptoms resulting in an overall AGE incidence of 24.7 per 100 person-weeks [95% confidence interval (CI): 22.4; 27.1]. In total, 20 NoV-positive AGE cases (5.2% of those tested) were identified at an incidence of 1.1 per 100 person-weeks (95% CI: 0.7; 1.7). NoV-positive samples belonged mostly to genogroup GII (18, 85.7%); None of the 13 samples sequenced belonged to genotype GII.4. Clinical severity of AGE was higher for NoV-positive than for NoV-negative cases (mean modified Vesikari Score 6.8 vs 4.9) with more cases classified as severe or moderate (25% vs 6.8%). In total, 80% of NoV-positive participants (vs 38.9% in NoV-negative) reported at least moderate impact on travel plans.

CONCLUSIONS

AGE is a prevalent disease amongst travellers with a small proportion associated with NoV. Post-travel stool sample collection timing might have influenced the low number of NoV cases detected; however, NoV infections resulted in high clinical severity and impact on travel plans. These results may contribute to targeted vaccine development and the design of future studies on NoV epidemiology.

Prevalence and genotype distribution of norovirus in Ningxia Hui Autonomous Region, China, from 2011 to 2022

The norovirus (NoV) genome is diverse. Therefore, this study explored the epidemiological characteristics and genetic features of NoV in Ningxia Hui Autonomous Region, China, from 2011 to 2022 to clarify the genetic diversity in this region. Stool samples were screened for NoV and then sequenced and genotyped. In total, 1,788 of 13,083 specimens were NoV -positive (13.67%); 204 (1.56%) and 1,584 (12.11%) cases were GI and GII, respectively. Additionally, 559 were NoV infection with other viruses (4.27%), primarily with rotavirus (277/559, 49.55%). The NoV incidence rate was the highest among children aged 0-2 years (18.09%, 1054/5,828) and lowest among adults aged 45-64 years (110/1,495, 7.36%); it was also higher in the winter and spring than in the other seasons. GI.3[P3] was the dominant GI genotype. The dominant GII genotype changed roughly every two years. In the GII group, GII.4 was the most common genotype (46.79%), followed by GII.3 (21.34%), GII.2 (12.34%), and GII.17 (9.77%). There were three variants of GII.4 Den Haag, GII.4 New Orleans and GII.4 Sydney identified in the detected GII.4 strains, with GII.4 Sydney dominating. The GII.4 (87.36%), GII.3 (86.35%), and GII.2 (72.92%) strains were primarily detected in children, whereas it was the GII.17 (52.63%) strain in adults. Overall, the NoV genotypes in the Ningxia Hui Autonomous Region were diverse. Primarily, GII groups were dominant, but this changed over time.

Prevalence and associated factors of norovirus infections among patients with diarrhea in the Amhara national regional state, Ethiopia

BACKGROUND

Noroviruses (NoVs) are the leading cause of diarrheal disease among all age groups worldwide, with an increased burden in developing countries. As there is no surveillance, epidemiological data is limited in Ethiopia. Hence, this study aimed to investigate the prevalence and associated factors of NoV infection among patients with diarrhea in the Amhara National Regional State, Ethiopia.

METHODS

A prospective health facility-based cross-sectional study was conducted from May 2021 to November 2021. A total of 550 study participants of all age groups with symptoms of diarrhea were proportionately assigned to the four study areas, area with three health facilities. Study participants were systematically sampled in each health facility. A fecal sample from each case was collected. The RNA was extracted and tested for NoV by one-step RT-PCR. Sociodemographic and other variables were gathered using a pre-tested questionnaire. A descriptive analysis was performed. Both binary and multiple logistic regressions were utilized to identify factors associated with NoV infection. Variables with a p-value < 0.05 in the final model were considered statistically significant.

RESULTS

Five hundred nineteen out of 550 samples were analyzed (94.4% response rate). The overall prevalence of NoV was 8.9% (46/519). The positivity rates were higher among the elderly (33.3%) and under-5 children (12.5%). Both genogroup I and genogroup II (GII) were identified, with GII being the predominant, at 82.6% (38/46). Of all participants, only 20% reported a history of vomiting. Norovirus infection was more prevalent among participants from Debre Tabor (AOR = 4, 95%CI: 1.2-14) and Bahir Dar areas (AOR = 3.6, 95%CI: 1.04-11) compared to Debre Markos. Additionally, older adults (AOR = 7, 95% CI: 2-24) and under-5 children (AOR = 3.5, 95% CI: 2.8-12) were disproportionately affected compared to adults. The previous history of diarrhea (AOR = 3.6, 95% CI: 1.7-7) was a significant factor contributing to NoV infections. Moreover, the odds of NoV infection were higher among individuals with a high frequency of diarrhea (AOR = 15.3, 95%CI: 7.6-43) and vomiting (AOR = 3.5, 95%CI: 1.5-8).

CONCLUSIONS

The prevalence of NoV was considerably high, with the predominance of NoV-GII. The positivity rate was higher among the extreme age groups and varied across the study areas. To obtain a comprehensive understanding of the virus`s epidemiology and its genetic diversity, further research is warranted.

Rotavirus outbreaks in China, 1982-2021: a systematic review

Background

Rotavirus is globally recognized as an important cause of acute gastroenteritis in young children. Whereas previous studies focused more on sporadic diarrhea, the epidemiological characteristics of rotavirus outbreaks have not been systematically understood.

Methods

This systematic review was carried out according to the Preferred Reporting Items for Systematic Review and Meta-Analysis standards, WANFANG, China National Knowledge Infrastructure (CNKI), PubMed, and Web of Science databases were searched from database inception to February 20, 2022. We used SPSS 21.0 statistical software for data analysis, RStudio1.4.1717, and ArcGIS trial version for plotting bar graphs and maps.

Results

Among 1,596 articles, 78 were included, with 92 rotavirus outbreaks and 96,128 cases. Most outbreaks (67.39%, 62/92) occurred in winter and spring. The number of rotavirus outbreaks reported in the eastern region was more than that in the western region. Outbreaks were most commonly reported in villages (33/92, 35.87%), followed by hospitals (19, 20.65%). The outbreak duration was longer in factories and workers' living places, and villages, while it was shorter in hospitals. Waterborne transmission was the main transmission mode, with the longest duration and the largest number of cases. Rotavirus groups were identified in 66 outbreaks, with 40 outbreaks (60.61%) caused by Group B rotaviruses and 26 outbreaks (39.39%) caused by Group A rotaviruses. Significant differences were found in duration, number of cases, settings, population distribution, and transmission modes between Groups A and B rotavirus outbreaks.

Conclusion

Rotavirus is an important cause of acute gastroenteritis outbreaks in China. It should also be considered in the investigation of acute gastroenteritis outbreaks, especially norovirus-negative outbreaks.

Diverse genotypes of norovirus genogroup I and II contamination in environmental water in Thailand during the COVID-19 outbreak from 2020 to 2022

Noroviruses (NoVs) are the most significant viral pathogens associated with waterborne and foodborne outbreaks of nonbacterial acute gastroenteritis in humans worldwide. This study aimed to investigate the prevalence and diversity of NoVs contaminated in the environmental water in Chiang Mai, Thailand. A total of 600 environmental water samples were collected from ten sampling sites in Chiang Mai from July 2020 to December 2022. The presence of NoV genogroups I (GI), GII, and GIV were examined using real-time RT-PCR assay. The genotype of the virus was determined by nucleotide sequencing and phylogenetic analysis. The results showed that NoV GI and GII were detected at 8.5% (51/600) and 11.7% (70/600) of the samples tested, respectively. However, NoV GIV was not detected in this study. NoV circulated throughout the year, with a higher detection rate during the winter season. Six NoV GI genotypes (GI.1-GI.6) and eight NoV GII genotypes (GII.2, GII.3, GII.7, GII.8, GII.10, GII.13, GII.17, and GII.21) were identified. Among 121 NoV strains detected, GII.17 was the most predominant genotype (24.8%, 30 strains), followed by GII.2 (21.5%, 26 strains), GI.3 (17.4%, 21 strains), and GI.4 (16.5%, 20 strains). Notably, NoV GII.3, GII.7, GII.8, and GII.10 were detected for the first time in water samples in this area. This study provides insight into the occurrence and seasonal pattern of NoV along with novel findings of NoV strains in environmental water in Thailand during the COVID-19 outbreak. Our findings emphasize the importance of further surveillance studies to monitor viral contamination in environmental water.

Comparing the Efficacy of Ondansetron, Domperidone, and Metoclopramide in Treating Vomiting in Pediatric Patients With Acute Gastroenteritis: A Network Meta-Analysis

This network meta-analysis compared the efficacy of ondansetron, domperidone, and metoclopramide in managing vomiting in pediatric acute gastroenteritis. A comprehensive literature search was conducted across multiple databases, including PubMed, Cochrane Library, Web of Science, and Embase, from their inception to July 25, 2024. Additionally, Google Scholar was searched to identify further relevant studies. In total, 19 randomized controlled trials (RCTs) were included. The primary outcome was cessation of vomiting. The results indicated that ondansetron was significantly more effective than placebo in achieving cessation of vomiting. While domperidone and metoclopramide also showed improved efficacy compared to placebo, these differences were not statistically significant. Ondansetron emerged as the most effective intervention, followed by domperidone and metoclopramide. These findings have significant clinical implications, suggesting that ondansetron should be the preferred antiemetic for pediatric acute gastroenteritis. Its use may reduce the need for intravenous rehydration and hospitalization, potentially improving patient outcomes and reducing healthcare costs. However, the study has limitations, including a lack of data on secondary outcomes and safety profiles of the interventions. Future prospective, multicenter studies are needed to assess both the efficacy and safety of these antiemetics comprehensively in pediatric acute gastroenteritis.

Association of fucosyltransferase 2 gene polymorphism with the susceptibility to norovirus infection in Han Chinese population

Fucosyltransferase 2 (FUT2) gene, which regulates the formation of Histoblood group antigens, could determine the human susceptibility to norovirus. This study aimed to investigate the correlation between FUT2 gene polymorphism and susceptibility to norovirus gastroenteritis in Han Chinese population. A total of 212 children patients with acute gastroenteritis were enrolled. The stool and serum samples were collected respectively. We used the qPCR method to detect the norovirus infection status from the stool samples, and we used serum samples to detect the FUT2 polymorphism. A case-control study was conducted to investigate the three common SNPs polymorphisms (rs281377, rs1047781, and rs601338) of FUT2 gene with sanger sequencing method. The results indicated that the homozygous genotypes and mutant allele of rs1047781 (A385T) would downgrade the risk of norovirus gastroenteritis in Chinese Han population (AA vs. TT, odds ratio [OR] = 0.098, 95% confidence interval [CI] = 0.026-0.370, p = 0.001; AA + AT vs. TT, OR = 0.118. 95% CI = 0.033-0.424, p = 0.001; A vs. T, OR = 0.528, 95% CI = 0.351-0.974, p = 0.002). There were no significant difference of rs281377 (C357T) and rs601338 (G428A) polymorphisms between norovirus positive and norovirus negative groups (p > 0.05). The haplotype T-T-G was less susceptible (OR = 0.49, 95% CI = 0.31-0.79, p = 0.0034) to norovirus infection compared to other haplotypes. Our results investigated the relationship between the FUT2 gene polymorphisms and norovirus susceptibility in Han Chinese population, and firstly revealed that children with homozygous genotypes and mutant alleles of FUT2 rs1047781 (A385T) were less susceptible to norovirus gastroenteritis.

Wastewater surveillance for viral pathogens: A tool for public health

A focus on water quality has intensified globally, considering its critical role in sustaining life and ecosystems. Wastewater, reflecting societal development, profoundly impacts public health. Wastewater-based epidemiology (WBE) has emerged as a surveillance tool for detecting outbreaks early, monitoring infectious disease trends, and providing real-time insights, particularly in vulnerable communities. WBE aids in tracking pathogens, including viruses, in sewage, offering a comprehensive understanding of community health and lifestyle habits. With the rise in global COVID-19 cases, WBE has gained prominence, aiding in monitoring SARS-CoV-2 levels worldwide. Despite advancements in water treatment, poorly treated wastewater discharge remains a threat, amplifying the spread of water-, sanitation-, and hygiene (WaSH)-related diseases. WBE, serving as complementary surveillance, is pivotal for monitoring community-level viral infections. However, there is untapped potential for WBE to expand its role in public health surveillance. This review emphasizes the importance of WBE in understanding the link between viral surveillance in wastewater and public health, highlighting the need for its further integration into public health management.

Global prevalence of norovirus gastroenteritis after emergence of the GII.4 Sydney 2012 variant: a systematic review and meta-analysis

Introduction

Norovirus is widely recognized as a leading cause of both sporadic cases and outbreaks of acute gastroenteritis (AGE) across all age groups. The GII.4 Sydney 2012 variant has consistently prevailed since 2012, distinguishing itself from other variants that typically circulate for a period of 2-4 years.

Objective

This review aims to systematically summarize the prevalence of norovirus gastroenteritis following emergence of the GII.4 Sydney 2012 variant.

Methods

Data were collected from PubMed, Embase, Web of Science, and Cochrane databases spanning the period between January 2012 and August 2022. A meta-analysis was conducted to investigate the global prevalence and distribution patterns of norovirus gastroenteritis from 2012 to 2022.

Results

The global pooled prevalence of norovirus gastroenteritis was determined to be 19.04% (16.66-21.42%) based on a comprehensive analysis of 70 studies, which included a total of 85,798 sporadic cases with acute gastroenteritis and identified 15,089 positive cases for norovirus. The prevalence rate is higher in winter than other seasons, and there are great differences among countries and age groups. The pooled attack rate of norovirus infection is estimated to be 36.89% (95% CI, 36.24-37.55%), based on a sample of 6,992 individuals who tested positive for norovirus out of a total population of 17,958 individuals exposed during outbreak events.

Conclusion

The global prevalence of norovirus gastroenteritis is always high, necessitating an increased emphasis on prevention and control strategies with vaccine development for this infectious disease, particularly among the children under 5 years old and the geriatric population (individuals over 60 years old).

Establishment of a Nucleic Acid Detection Method for Norovirus GII.2 Genotype Based on RT-RPA and CRISPR/Cas12a-LFS

To establish a rapid detection method for norovirus GII.2 genotype, this study employed reverse transcription recombinase polymerase amplification (RT-RPA) combined with CRISPR/Cas12a and lateral flow strip (RT-RPA-Cas12a-LFS). Here, the genome of norovirus GII.2 genotype was compared to identify highly conserved sequences, facilitating the design of RT-RPA primers and crRNA specific to the conserved regions of norovirus GII.2. Subsequently, the reaction parameters of RT-RPA were optimized and evaluated using agar-gel electrophoresis and LFS. The results indicate that the conserved sequences of norovirus GII.2 were successfully amplified through RT-RPA at 37°C for 25 minutes. Additionally, CRISPR/Cas12a-mediated cleavage detection was achieved through LFS at 37°C within 10 minutes using the amplification products as templates. Including the isothermal amplification reaction time, the total time is 35 minutes. The established RT-RPA-Cas12a-LFS method demonstrated specific detection of norovirus GII.2, yielding negative results for other viral genomes, and exhibited an excellent detection limit of 10 copies/μl. The RT-RPA-Cas12a-LFS method was further compared with qRT-PCR by analyzing 60 food-contaminated samples. The positive conformity rate was 100%, the negative conformity rate was 95.45%, and the overall conformity rate reached 98.33%. This detection method for norovirus GII.2 genotype is cost-effective, highly sensitive, specific, and easy to operate, offering a promising technical solution for field-based detection of the norovirus GII.2 genotype.

Improving the Detection and Understanding of Infectious Human Norovirus in Food and Water Matrices: A Review of Methods and Emerging Models

Human norovirus (HuNoV) is a leading global cause of viral gastroenteritis, contributing to numerous outbreaks and illnesses annually. However, conventional cell culture systems cannot support the cultivation of infectious HuNoV, making its detection and study in food and water matrices particularly challenging. Recent advancements in HuNoV research, including the emergence of models such as human intestinal enteroids (HIEs) and zebrafish larvae/embryo, have significantly enhanced our understanding of HuNoV pathogenesis. This review provides an overview of current methods employed for HuNoV detection in food and water, along with their associated limitations. Furthermore, it explores the potential applications of the HIE and zebrafish larvae/embryo models in detecting infectious HuNoV within food and water matrices. Finally, this review also highlights the need for further optimization and exploration of these models and detection methods to improve our understanding of HuNoV and its presence in different matrices, ultimately contributing to improved intervention strategies and public health outcomes.

Microbiological hazard identification in river waters used for recreational activities

Pathogenic bacteria, viruses, and parasites can cause waterborne disease outbreaks. The study of coastal water quality contributes to identifying potential risks to human health and to improving water management practices. The Río de la Plata River, a wide estuary in South America, is used for recreational activities, as a water source for consumption and as a site for sewage discharges. In the present study, as the first step of a quantitative microbial risk assessment of the coastal water quality of this river, a descriptive study was performed to identify the microbial pathogens prevalent in its waters and in the sewage discharged into the river. Two sites, representing two different potential risk scenarios, were chosen: a heavily polluted beach and an apparently safe beach. Conductivity and fecal contamination indicators including enterococci, Escherichia coli, F + RNA bacteriophages, and human polyomaviruses showed high levels. Regarding enterococci, differences between sites were significant (p-values <0.001). 93.3% and 56.5% of the apparently safe beach exceeded the recreational water limits for E. coli and enterococci. Regarding pathogens, diarrheagenic E. coli, Salmonella, and noroviruses were detected with different frequencies between sites. The parasites Cryptosporidium spp. and Giardia duodenalis were frequently detected in both sites. The results regarding viral, bacterial, and parasitic pathogens, even without correlation with conventional indicators, showed the importance of monitoring a variety of microorganisms to determine water quality more reliably and accurately, and to facilitate further studies of health risk assessment. The taxonomic description of microbial pathogens in river waters allow identifying the microorganisms that infect the population living on its shores but also pathogens not previously reported by the clinical surveillance system.

Human Norovirus Surrogate Is Highly Stable in Berry Smoothies and under In Vitro Simulated Digestion

Human noroviruses are major causes of foodborne outbreaks linked to berries. The overall goal of this study was to investigate the persistence of a human norovirus surrogate, Tulane virus (TV), in berry smoothies and under simulated digestion through the gastrointestinal track. Two types of smoothies were prepared from blueberries and strawberries. Tulane virus was spiked into each smoothie and incubated either at 37 or 4 °C for 2, 60, and 120 min. Furthermore, the virus-spiked smoothies were subjected to sequential oral (2 min), gastric (10 and 60 min), and intestinal (15 and 120 min) digestion according to the standardized INFOGEST model. Quantification of infectious TV was carried out using the TCID50 assay. At 4 °C, in both berry smoothies, TV infectivity did not show significant changes throughout the 120 min period. At 37 °C, TV infectivity showed significant reduction (~0.5 log TCID50/mL) only in blueberry smoothies starting at 60 min. During the oral, gastric, and intestinal digestion phases, the mean log reduction in TV infectivity in blueberry did not exceed ~0.5 log, while infectious TV in strawberry smoothies under all phases was stable. Given the notable stability of infectious viruses in berry smoothies and the gastrointestinal tract, prevention of norovirus contamination of berries is paramount to reduce virus outbreaks linked to berries.

Viral gastroenteritis

Since the discovery of norovirus in 1972 as a cause of what was contemporarily known as acute infectious non-bacterial gastroenteritis, scientific understanding of the viral gastroenteritides has continued to evolve. It is now recognised that a small number of viruses are the predominant cause of acute gastroenteritis worldwide, in both high-income and low-income settings. Although treatment is still largely restricted to the replacement of fluid and electrolytes, improved diagnostics have allowed attribution of illness, enabling both targeted treatment of individual patients and prioritisation of interventions for populations worldwide. Questions remain regarding specific genetic and immunological factors underlying host susceptibility, and the optimal clinical management of patients who are susceptible to severe or prolonged manifestations of disease. Meanwhile, the worldwide implementation of rotavirus vaccines has led to substantial reductions in morbidity and mortality, and spurred interest in vaccine development to diminish the impact of the most prevalent viruses that are implicated in this syndrome.

Estimation of Norovirus infections in Japan: An application of wastewater-based epidemiology for enteric disease assessment

Noroviruses of genogroup I (NoV GI) and NoV GII are the primary causes of acute gastroenteritis (AGE) in developed countries. However, asymptomatic and untested NoV infections lead to an underestimation of AGE cases, and the lack of mandatory viral identification in clinical cases hinders precise estimation of NoV infections. Back estimation of NoV infections in the community using a wastewater-based epidemiology (WBE) approach can provide valuable insights into the disease's extent, progression, and epidemiology, aiding in developing effective control strategies. This study employed a one-step reverse transcription-quantitative PCR to quantify NoVs GI and GII in wastewater samples (n = 83) collected twice a week from June 2022 to March 2023 in Japan. All samples from the Winter-Spring (n = 27) tested positive for NoV GI and GII RNA, while 73 % and 88 % of samples from the Summer-Autumn (n = 56) were positive for NoV GI and NoV GII RNA, respectively. Significantly higher concentrations of NoV GI/GII RNA were found in the Winter-Spring season compared to the Summer-Autumn season. NoV RNA was consistently detected in wastewater throughout the year, demonstrating the persistence of AGE cases in the catchment, suggesting an endemic NoV infection. Estimates of NoV infection incorporated viral RNA concentrations, wastewater parameters, and signal persistence in a mass balance equation using Monte Carlo Simulation. The median estimated NoV GI infections per 100,000 population for Summer-Autumn was 133 and for the Winter-Spring season, it was 881. Estimated NoV GII infections were 1357 for Summer-Autumn and 11,997 for the Winter-Spring season per 100,000 population. The estimated NoV infections exceeded by 3.2 and 23.9 folds than the reported AGE cases in Summer-Autumn and Winter-Spring seasons, respectively. The seasonal trend of estimated NoV infections closely matched that of AGE cases, highlighting the utility of WBE in understanding the epidemiology of enteric infections.

A broad wastewater screening and clinical data surveillance for virus-related diseases in the metropolitan Detroit area in Michigan

BACKGROUND

Periodic bioinformatics-based screening of wastewater for assessing the diversity of potential human viral pathogens circulating in a given community may help to identify novel or potentially emerging infectious diseases. Any identified contigs related to novel or emerging viruses should be confirmed with targeted wastewater and clinical testing.

RESULTS

During the COVID-19 pandemic, untreated wastewater samples were collected for a 1-year period from the Great Lakes Water Authority Wastewater Treatment Facility in Detroit, MI, USA, and viral population diversity from both centralized interceptor sites and localized neighborhood sewersheds was investigated. Clinical cases of the diseases caused by human viruses were tabulated and compared with data from viral wastewater monitoring. In addition to Betacoronavirus, comparison using assembled contigs against a custom Swiss-Prot human virus database indicated the potential prevalence of other pathogenic virus genera, including: Orthopoxvirus, Rhadinovirus, Parapoxvirus, Varicellovirus, Hepatovirus, Simplexvirus, Bocaparvovirus, Molluscipoxvirus, Parechovirus, Roseolovirus, Lymphocryptovirus, Alphavirus, Spumavirus, Lentivirus, Deltaretrovirus, Enterovirus, Kobuvirus, Gammaretrovirus, Cardiovirus, Erythroparvovirus, Salivirus, Rubivirus, Orthohepevirus, Cytomegalovirus, Norovirus, and Mamastrovirus. Four nearly complete genomes were recovered from the Astrovirus, Enterovirus, Norovirus and Betapolyomavirus genera and viral species were identified.

CONCLUSIONS

The presented findings in wastewater samples are primarily at the genus level and can serve as a preliminary "screening" tool that may serve as indication to initiate further testing for the confirmation of the presence of species that may be associated with human disease. Integrating innovative environmental microbiology technologies like metagenomic sequencing with viral epidemiology offers a significant opportunity to improve the monitoring of, and predictive intelligence for, pathogenic viruses, using wastewater.

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.

Murine norovirus infection of macrophages induces intrinsic apoptosis as the major form of programmed cell death

Human norovirus is the leading cause of acute gastroenteritis worldwide, however despite the significance of this pathogen, we have a limited understanding of how noroviruses cause disease, and modulate the innate immune response. Programmed cell death (PCD) is an important part of the innate response to invading pathogens, but little is known about how specific PCD pathways contribute to norovirus replication. Here, we reveal that murine norovirus (MNV) virus-induced PCD in macrophages correlates with the release of infectious virus. We subsequently show, genetically and chemically, that MNV-induced cell death and viral replication occurs independent of the activity of inflammatory mediators. Further analysis revealed that MNV infection promotes the cleavage of apoptotic caspase-3 and PARP. Correspondingly, pan-caspase inhibition, or BAX and BAK deficiency, perturbed viral replication rates and delayed virus release and cell death. These results provide new insights into how MNV harnesses cell death to increase viral burden.

Prevalence and Characterization of Gastroenteritis Viruses among Hospitalized Children during a Pilot Rotavirus Vaccine Introduction in Vietnam

Rotavirus (RV), norovirus (NoV), sapovirus (SaV), and human astrovirus (HAstV) are the most common viral causes of gastroenteritis in children worldwide. From 2016 to 2021, we conducted a cross-sectional descriptive study to determine the prevalence of these viruses in hospitalized children under five years old in Nam Dinh and Thua Thien Hue provinces in Vietnam during the pilot introduction of the RV vaccine, Rotavin-M1 (POLYVAC, Hanoi, Vietnam). We randomly selected 2317/6718 (34%) acute diarrheal samples from children <5 years of age enrolled at seven sentinel hospitals from December 2016 to May 2021; this period included one year surveillance pre-vaccination from December 2016 to November 2017. An ELISA kit (Premier Rotaclone®, Meridian Bioscience, Inc., Cincinnati, OH, USA) was used to detect RV, and two multiplex real-time RT-PCR assays were used for the detection of NoV, SaV and HAstV. The prevalence of RV (single infection) was reduced from 41.6% to 22.7% (p < 0.0001) between pre- and post-vaccination periods, while the single NoV infection prevalence more than doubled from 8.8% to 21.8% (p < 0.0001). The SaV and HAstV prevalences slightly increased from 1.9% to 3.4% (p = 0.03) and 2.1% to 3.3% (p = 0.09), respectively, during the same period. Viral co-infections decreased from 7.2% to 6.0% (p = 0.24), mainly due to a reduction in RV infection. Among the genotypeable samples, NoV GII.4, SaV GI.1, and HAstV-1 were the dominant types, representing 57.3%, 32.1%, and 55.0% among the individual viral groups, respectively. As the prevalence of RV decreases following the national RV vaccine introduction in Vietnam, other viral pathogens account for a larger proportion of the remaining diarrhea burden and require continuing close monitoring.

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.

The predominance of recombinant Norovirus GII.4Sydney[P16] strains in children less than 5 years of age with acute gastroenteritis in Tehran, Iran, 2021-2022

The present study was aimed to both detect emerging noroviruses and investigate RdRp and VP1-based dual typing of circulating noroviruses in hospitalized children less than 5 years of age with acute gastroenteritis (AGE) in Iran. For this purpose, a total of 200 stool specimens were screened during 2021-2022 by real-time RT-PCR for genogroup I and II (GI and GII) and dual-typed by sequence analysis of PCR products, using a web-based norovirus Typing Tool and phylogenetic analysis. The GI and GII noroviruses were detected in 20% of 200 specimens. The GII.4 norovirus was found to be the most common VP1 genotype (53%) followed by GII.8 (32%), GII.7 (6%), GII.17 (6%), and GII.3 (3%). The GII.P16 norovirus was also found as the predominant RdRp type (53%) followed by GII.P8 (32%), GII.P7 (6%), GII.P17 (6%), and GII.P31 (3%). To our knowledge, this is the first report that highlights the dominancy of recombinant norovirus GII.4Sydney[P16] and newly emerging of norovirus GII.8 [P8], GII.17 [P17] and GII.3 [P16] in Iran. These findings further indicate inter-genotype recombinant strains of noroviruses.

Genome characterisation of norovirus GII.P17-GII.17 detected during a large gastroenteritis outbreak in Romania in 2021

Norovirus (NoV) is one of the leading causes of acute gastroenteritis worldwide. Genotype GII.P17-G.II.17 emerged in Asia between 2013 and 2015 and transiently replaced the GII.4 Sydney 2012 variant circulating at that time. We present the genome characterisation of a GII.P17-GII.17 strain causing a large outbreak in Romania in 2021. Our study shows that the 2021 strain belongs to a novel cluster of genotype GII.17, different from the two previously recognised P.17 clusters. Distinctive substitutions in predicted conformational epitopes of VP1 were identified for this new cluster. Also, our phylogenetic analysis showed the existence of another P.17 cluster grouping strains from France and Canada.

Factors driving norovirus transmission in long-term care facilities: A case-level analysis of 107 outbreaks

Norovirus is the most common cause of gastroenteritis outbreaks in long-term care facilities (LTCFs) in the United States, causing a high burden of disease in both residents and staff. Understanding how case symptoms and characteristics contribute to norovirus transmission can lead to more informed outbreak control measures in LTCFs. We examined line lists for 107 norovirus outbreaks that took place in LTCFs in five U.S. states from 2015 to 2019. We estimated the individual effective reproduction number, Ri, to quantify individual case infectiousness and examined the contribution of vomiting, diarrhea, and being a resident (vs. staff) to case infectiousness. The associations between case characteristics and Ri were estimated using a multivariable, log-linear mixed model with inverse variance weighting. We found that cases with vomiting infected 1.28 (95 % CI: 1.11, 1.48) times the number of secondary cases compared to cases without vomiting, and LTCF residents infected 1.31 (95 % CI: 1.15, 1.50) times the number of secondary cases compared to staff. There was no difference in infectiousness between cases with and without diarrhea (1.07; 95 % CI: 0.90, 1.29). This suggests that vomiting, particularly by LTCF residents, was a primary driver of norovirus transmission. These results support control measures that limit exposure to vomitus during norovirus outbreaks in LTCFs.

Molecular Evolution of RNA-Dependent RNA Polymerase Region in Norovirus Genogroup I

Norovirus is the leading viral agent of gastroenteritis in humans. RNA-dependent RNA polymerase (RdRp) is essential in the replication of norovirus RNA. Here, we present a comprehensive evolutionary analysis of the norovirus GI RdRp gene. Our results show that the norovirus GI RdRp gene can be divided into three groups, and that the most recent common ancestor was 1484. The overall evolutionary rate of GI RdRp is 1.821 × 10-3 substitutions/site/year. Most of the amino acids of the GI RdRp gene were under negative selection, and only a few positively selected sites were recognized. Amino acid substitutions in the GI RdRp gene accumulated slowly over time. GI.P1, GI.P3 and GI.P6 owned the higher evolutionary rates. GI.P11 and GI.P13 had the faster accumulation rate of amino acid substitutions. GI.P2, GI.P3, GI.P4, GI.P6 and GI.P13 presented a strong linear evolution. These results reveal that the norovirus GI RdRp gene evolves conservatively, and that the molecular evolutionary characteristics of each P-genotype are diverse. Sequencing in RdRp and VP1 of norovirus should be advocated in the surveillance system to explore the effect of RdRp on norovirus activity.

Rapid screening for antigenic characterization of GII.17 norovirus strains with variations in capsid gene

The emergence of the novel GII.17 Kawasaki 2014 norovirus variant raising the interest of the public, has replaced GII.4 as the predominant cause of noroviruses outbreaks in East Asia during 2014–2015. Antigenic variation of the capsid protein is considered as one of the key mechanisms of norovirus evolution. In this study, we screened a panel of GII.17 mutants. First, we produced norovirus P proteins using cell-free protein synthesis (CFPS) system, comparing the results to pure proteins expressed in a cell-based system. Next, we determined the binding capability of specific monoclonal antibody (mAb) 2D11 using a unique set of wild-type GII.17 strains. Results of the EIA involving a panel of mutant cell-free proteins indicated that Q298 was the key residue within loop 1. These data highlighted the essential residues in the linear antibody binding characteristics of novel GII.17. Furthermore, it supported the CFPS as a promising tool for rapidly screening mutants via the scalable expression of norovirus P proteins.

Epidemiology of Norovirus in the First 2 Years of Life in an Australian Community-based Birth Cohort

BACKGROUND

Noroviruses are a leading cause of acute gastroenteritis across all age groups in Australia. We explored the epidemiology of symptomatic and asymptomatic norovirus infection and assessed risk factors and the related healthcare burden in Australian children during their first 2 years of life.

METHODS

Participants in the Observational Research in Childhood Infectious Diseases birth cohort provided weekly stool swabs, daily gastrointestinal symptoms (vomiting and loose stools) observations and healthcare data. Swabs were batch-tested for norovirus genogroups (GI and GII) using real-time polymerase chain reaction assays.

RESULTS

Overall, 158 children returned 11,124 swabs. There were 221 infection episodes, of which 183 (82.8%) were GII. The incidence rate was 0.90 infections per child-year [95% confidence interval (CI): 0.74-1.09]. The symptomatic infection incidence rate was 0.39 per child-year (95% CI: 0.31-0.48), peaking between ages 6 and 11 months [0.58 (95% CI: 0.41-0.81)]. Incidence increased significantly with age and childcare attendance. Of 209 episodes with symptom diary data, 82 (39.2%) were symptomatic; of these 70 (85.4%) were associated with vomiting and 29 (35.4%) with diarrhea. Forty-one percent of symptomatic episodes required healthcare, including 4 emergency department presentations and 1 hospitalization. Children with initial infections had almost twice the risk of seeking primary healthcare compared to subsequent infections (adjusted risk ratio 1.92; 95% CI: 1.01-3.65).

CONCLUSIONS

Norovirus infections, particularly GII, are common in Australian children 6-23 months of age. Estimates of norovirus incidence, including symptomatic infections and healthcare utilization in community settings in young children, are crucial for planning norovirus vaccine programs and determining vaccine effectiveness.

Norovirus Infection in Young Nicaraguan Children Induces Durable and Genotype-Specific Antibody Immunity

There are significant challenges to the development of a pediatric norovirus vaccine, mainly due to the antigenic diversity among strains infecting young children. Characterizing human norovirus serotypes and understanding norovirus immunity in naïve children would provide key information for designing rational vaccine platforms. In this study, 26 Nicaraguan children experiencing their first norovirus acute gastroenteritis (AGE) episode during the first 18 months of life were investigated. We used a surrogate neutralization assay that measured antibodies blocking the binding of 13 different norovirus virus-like particles (VLPs) to histo-blood group antigens (HBGAs) in pre- and post-infection sera. To assess for asymptomatic norovirus infections, stools from asymptomatic children were collected monthly, screened for norovirus by RT-qPCR and genotyped by sequencing. Seroconversion of an HBGA-blocking antibody matched the infecting genotype in 25 (96%) of the 26 children. A subset of 13 (50%) and 4 (15%) of the 26 children experienced monotypic GII and GI seroconversion, respectively, strongly suggesting a type-specific response in naïve children, and 9 (35%) showed multitypic seroconversion. The most frequent pairing in multitypic seroconversion (8/12) were GII.4 Sydney and GII.12 noroviruses, both co-circulating at the time. Blocking antibody titers to these two genotypes did not correlate with each other, suggesting multiple exposure rather than cross-reactivity between genotypes. In addition, GII titers remained consistent for at least 19 months post-infection, demonstrating durable immunity. In conclusion, the first natural norovirus gastroenteritis episodes in these young children were dominated by a limited number of genotypes and induced responses of antibodies blocking binding of norovirus VLPs in a genotype-specific manner, suggesting that an effective pediatric norovirus vaccine likely needs to be multivalent and include globally dominant genotypes. The duration of protection from natural infections provides optimism for pediatric norovirus vaccines administered early in life.

Molecular epidemiology and characterization of norovirus and sapovirus in pediatric patients with acute diarrhea in Thailand, 2019-2020

BACKGROUND

Human enteric pathogens in the family Caliciviridae including norovirus (NoV) and sapovirus (SaV) are associated with acute diarrheal disease globally and are considered as one of the viruses with high genetic diversity.

METHODS

In order to investigate the epidemiology of NoV and SaV in pediatric patients with acute diarrhea in Chiang Mai, Thailand from January 2019 to December 2020, a total of 675 stool specimens were collected and examined for the presence of NoV and SaV by RT-multiplex PCR.

RESULTS

126 (18.7 %) and 6 (0.9 %) stool samples were positive for NoV and SaV, respectively. Mixed infection of NoV and SaV was detected in one patient (0.2 %). Among 10 different NoV strains detected in this study, NoV genogroup II genotype 4 (GII.4) Sydney 2012 was the most predominant genotype (51.2 %) followed by GII.3, GII.2, GII.6, GII.12, GII.7, GII.17, GI.4, GII.14, and GI.3. Interestingly, monthly distribution of NoV genotypes revealed that NoV GII.3 increased dramatically in August 2019, suggesting an outbreak of NoV GII.3 might occur in the community. In addition, 3 genotypes of SaV were detected in this study with SaV GI.1 being the most common genotype (71.4 %) followed by GI.2 and GII.5 (each at 14.3 %).

CONCLUSIONS

This study demonstrates the prevalence and genetic diversity of NoV and SaV circulating in pediatric patients with acute gastroenteritis in Chiang Mai, Thailand during 2019-2020 and shows an emergence of NoV GII.3 infection in 2019.

Pooled prevalence and genetic diversity of norovirus in Africa: a systematic review and meta-analysis

Background

Noroviruses are the leading cause of acute gastroenteritis in all age groups globally. The problem is magnified in developing countries including Africa. These viruses are highly prevalent with high genetic diversity and fast evolution rates. With this dynamicity, there are no recent review in the past five years in Africa. Therefore, this review and meta-analysis aimed to assess the prevalence and genetic diversity of noroviruses in Africa and tried to address the change in the prevalence and genetic diverisity the virus has been observed in Africa and in the world.

Methods

Twenty-one studies for the pooled prevalence, and 11 out of the 21 studies for genetic characterization of norovirus were included. Studies conducted since 2006, among symptomatic cases of all age groups in Africa, conducted with any study design, used molecular diagnostic methods and reported since 2015, were included and considered for the main meta-analysis. PubMed, Cochrane Library, and Google Scholar were searched to obtain the studies. The quality the studies was assessed using the JBI assessment tool. Data from studies reporting both asymptomatic and symptomatic cases, that did not meet the inclusion criteria were reviewed and included as discussion points. Data was entered to excel and imported to STATA 2011 to compute the prevalence and genetic diversity. Heterogeneity was checked using I² test statistics followed by subgroup and sensitivity analysis. Publication bias was assessed using a funnel plot and eggers test that was followed by trim and fill analysis.

Result

The pooled prevalence of norovirus was 20.2% (95% CI: 15.91, 24.4). The highest (36.3%) prevalence was reported in Ghana. Genogroup II noroviruses were dominant and reported as 89.5% (95% CI: 87.8, 96). The highest and lowest prevalence of this genogroup were reported in Ethiopia (98.3%), and in Burkina Faso (72.4%), respectively. Diversified genotypes had been identified with an overall prevalence of GII. 4 NoV (50.8%) which was followed by GII.6, GII.17, GI.3 and GII.2 with a pooled prevalence of 7.7, 5.1, 4.6, and 4.2%, respectively.

Conclusion

The overall pooled prevalence of norovirus was high in Africa with the dominance of genogroup II and GII.4 genotype. This prevalence is comparable with some reviews done in the same time frame around the world. However, in Africa, an in increasing trained of pooled prevalence had been reported through time. Likewise, a variable distribution of non-GII.4 norovirus genotypes were reported as compared to those studies done in the world of the same time frame, and those previous reviews done in Africa. Therefore, continuous surveillance is required in Africa to support future interventions and vaccine programs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12985-022-01835-w.

The VP2 protein exhibits cross-interaction to the VP1 protein in norovirus GII.17

Norovirus is a major cause of acute gastroenteritis worldwide. Like the major capsid protein (VP1), the minor capsid protein (VP2) also contains a hypervariable domain. Generally, a hypervariable domain is functionally driven. However, many functions of VP2 remain unknown and worth exploring. Without sufficient sequences and an available crystallographic model, it is difficult to explore VP2's mysteries. As a helper of stabilizing and coordinating the formation of virus-like particles (VLPs), we asked whether VP2 interacted with the major capsid protein (VP1) in GII.17 and if so, what the key interaction residues were. Here, we reported cross-interaction among four strains represented four clusters of GII.17, and the VP1 interaction domain of VP2 (174-179aa) was found. However, the VP1 interaction domain of VP2 was not universal in different clusters of GII.17. VP2 might evolve in a different pattern from VP1. Additionally, in contrast to previous reports, we found that VP2 localized in the cytoplasm. More possibilities of VP2 should be further explored.

Diversity and distribution of Type VI Secretion System gene clusters in bacterial plasmids

Type VI Secretion System (T6SS) is a nanomolecular apparatus that allows the delivery of effector molecules through the cell envelope of a donor bacterium to prokaryotic and/or eukaryotic cells, playing a role in the bacterial competition, virulence, and host interaction. T6SS is patchily distributed in bacterial genomes, suggesting an association with horizontal gene transfer (HGT). In fact, T6SS gene loci are eventually found within genomic islands (GIs), and there are some reports in plasmids and integrative and conjugative elements (ICEs). The impact that T6SS may have on bacteria fitness and the lack of evidence on its spread mechanism led us to question whether plasmids could represent a key mechanism in the spread of T6SS in bacteria. Therefore, we performed an in-silico analysis to reveal the association between T6SS and plasmids. T6SS was mined on 30,660 plasmids from NCBI based on the presence of at least six T6SS core proteins. T6SS was identified in 330 plasmids, all belonging to the same type (T6SSⁱ), mainly in Proteobacteria (328/330), particularly in Rhizobium and Ralstonia. Interestingly, most genomes carrying T6SS-harboring plasmids did not encode T6SS in their chromosomes, and, in general, chromosomal and plasmid T6SSs did not form separate clades.

Knowledge, Awareness, and Prevention of Norovirus Infection among Kindergarten Parents in Chengdu, China

Human noroviruses (HuNoVs) are a leading cause of acute gastroenteritis among children in China. However, little is known about parents' knowledge of HuNoV infection and their understanding of how to prevent and control the disease. Therefore, we performed an exploratory survey to assess the level of knowledge of HuNoV infection among kindergarten parents. A cross-sectional survey was conducted by investigating kindergarteners' parents through an online self-administered questionnaire between October 2020 and November 2020 in Chengdu, China. A total of 771 questionnaires were received with valid responses, and 81.97% of respondents had heard about NoV before. Among parents who had heard about HuNoV before, they had a poor awareness of incubation period, duration, and high-incidence seasons of HuNoV infection. The respondents also had a low-level awareness of how to clean the places contaminated by vomitus or stool. The multiple-regression analysis confirmed that factors associated with good knowledge regarding HuNoV infection were level of education, occupation, history of infection, and HuNoV learning experience. The most expected approach to learn about HuNoV among parents was the internet, followed by knowledge training in kindergartens, community information, and television. This is the first study to assess kindergarten parents' knowledge and awareness of HuNoV infection. The survey results provide insights that would help in developing effective strategies and educational materials to prevent and control the disease.

Viral infection among children under the age of 5 with diarrhea in Shenyang from 2018 to 2020: A hospital-based study

Diarrhea is one of the leading causes of death among children, especially in the age under 5, but few studies are available on viral diarrhea in Shenyang. To understand the infection status and the relevant epidemiological characteristics of viral diarrhea and to fill gaps of the distribution of viruses across Shenyang in children under the age of 5 with diarrhea, from 2018 to 2020, stool specimens of children with diarrhea aged 0-59 months and surveillance data were collected in Sentinel Hospital of Shenyang. Specimens were then tested to determine the type of viruses, the seasonal and spatial patterns for major viruses were determined. Viruses were identified in 47.9% of the 897 samples from children with diarrhea. The main viruses of stool samples were rotavirus (16.9%, predominant type G9P[8]), calicivirus (14.7%), adenovirus (11.8%), and astrovirus (4.5%). Viral infections were mainly detected in the age of 0-12 months. In the area of Shenyang, Huanggu had the most cases (198, 22.1%), followed by Dadong (137, 15.3%) and Hunnan (135, 15.1%). The positive rate of viruses varied among patients of different ages, seasons, and regions. Public health entities and the government should develop corresponding measures for different age groups, seasons, and regions.