Detection and molecular characterization of noroviruses and sapoviruses in children admitted to hospital with acute gastroenteritis in Vietnam

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).

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.

Porcine Sapovirus in Northern Vietnam: Genetic Detection and Characterization Reveals Co-Circulation of Multiple Genotypes

Porcine sapovirus (PoSaV) has been reported in many countries over the world, which may cause gastroenteritis symptoms in pigs with all ages. There has been no report on PoSaV infection in Vietnam up to now. In this study, a total of 102 samples were collected from piglets, fattening pigs, and sows with diarrhea in several cities and provinces in northern Vietnam. The PoSaV genome was examined using polymerase chain reaction (PCR). Sequencing of the partial RNA-dependent RNA polymerase (RdRp) gene sequences (324 bp) was performed. Of the 102 tested samples, 10 (9.8%) and 7/20 (35%) were detected as positive for the PoSaV RdRp gene using the PCR method at the individual and farm levels, respectively. Genetic analysis of the partial RdRp gene region of about 324 bp indicated that the nucleotide identity of the current 10 Vietnamese viral strains ranged from 61.39% to 100%. Among the 10 strains obtained, 8 belonged to genotype III and the remaining 2 strains were clustered in genotype VIII. The Vietnamese genotype III viruses formed two sub-clusters. The Vietnamese PoSaV strains were closely related to PoSaVs reported in South Korea, Venezuela, and the Netherlands. This research was the first to describe PoSaV infection in northern Vietnam during 2022-2023.

An increase in prevalence of recombinant GII.3[P12] norovirus in sporadic acute diarrhea in children in Nizhny Novgorod, Russia, 2018-2021

Noroviruses are important etiological agents causing acute intestinal infection in humans. In the last decades, the most common norovirus genotype was GII.4 despite a significant genetic diversity among strains, while the active circulation of noroviruses with other genotypes was observed periodically. This study shows an increase in the detection rate of recombinant GII.3[P12] norovirus in Nizhny Novgorod, Russia, from 6.8% in 2018-2019 to 34.9% in 2020-2021. We performed a phylogenetic analysis based on the nucleotide sequences of noroviruses possessing this genotype obtained in this work, as well as presented in the GenBank database. It has been shown that the circulation of GII.3[P12] noroviruses in the study area was the result of several independent introductions, either directly from the Western Pacific region, or through the Asian part of Russia. The polyphyletic origin, the geographical expansion, and the growth of the epidemic significance of the recombinant GII.3[P12] noroviruses were noted.

Global molecular prevalence and genotype distribution of Sapovirus in children with gastrointestinal complications: A systematic review and meta-analysis

Sapovirus (SaV) is an emerging cause of children gastrointestinal complications such as acute gastroenteritis (AGE). The aim of the present systematic review and meta-analysis was to estimate the global prevalence of the SaV in children and association of infection with SaVs and AGE in children based on case-control studies. Four international databases (PubMed, Scopus, Web of Sciences and Google Scholar) were used to retrieve English-language studies published between January 2000 and December 2020. Comprehensive Meta-Analysis software was applied to estimate the overall prevalence, publication bias and heterogeneity index. The pooled prevalence of SaV infection among children with gastroenteritis was 3.4% [95% confidence interval (CI): 2.9%-3.9%] based on a random-effects meta-analysis. Genogroup I was the dominant genogroup of SaV in children with gastroenteritis [2.2% (95% CI: 1.6%-3.0%)], association analysis showed that SaV was associated with gastroenteritis [OR: 1.843 (95% CI: 1.27-2.66)]. Given the significant prevalence of the virus in children, it is necessary to pay more attention to this situation. Therefore, preventive health measures in children should be a priority.

Epidemiology of norovirus gastroenteritis in hospitalized children under five years old in western China, 2015-2019

OBJECTIVES

Norovirus is associated with one-fifth of all gastroenteritis cases, but basic epidemiological data is lacking, especially in developing countries. As long-term surveillance on norovirus gastroenteritis is scarce in western China, this study aims to update the epidemiological knowledge of norovirus gastroenteritis and to characterize the genotypes of norovirus strains.

METHODS

Stool samples were collected from hospitalized children under 5 years old with gastroenteritis in Chengdu, China. All samples were tested for norovirus as well as rotavirus, sapovirus, enteric adenovirus, and astrovirus by real-time RT-PCR. RdRp and VP1 genes were sequenced in norovirus-positive samples to investigate viral phylogenies.

RESULTS

Of the 1181 samples collected from 2015 to 2019, 242 (20.5%) were positive for norovirus. Among norovirus-positive cases, 65 cases had co-infection with another virus; norovirus/enteric adenovirus was most frequently detected (50.8%, 33/65). The highest positive rate was observed in children aged 13-18 months (23.7%, 68/287). Norovirus infection peaked in autumn (36.6%, 91/249), followed by summer (20.3%, 70/345). Pearson correlation analysis showed significant correlation between the norovirus-positive rate and humidity (r = 0.773, P < 0.05). GII.4 Sydney 2012 [P31] (48.5%, 79/163) and GII.3 [P12] (35.6%, 58/163) were the dominant norovirus strains.

CONCLUSIONS

Norovirus has become one of the most common causes of viral gastroenteritis in children under 5 years old in western China. Continuous monitoring is imperative for predicting the emergence of new epidemic strains and for current vaccine development.

Genetic recombination and diversity of sapovirus in pediatric patients with acute gastroenteritis in Thailand, 2010-2018

Background

Human sapovirus (SaV) is an etiologic agent of acute gastroenteritis (AGE) in all age groups worldwide. Genetic recombination of SaV has been reported from many countries. So far, none of SaV recombinant strain has been reported from Thailand. This study examined the genetic recombination and genotype diversity of SaV in children hospitalized with AGE in Chiang Mai, Thailand.

Methods

Stool samples were collected from children suffering from diarrhea who admitted to the hospitals in Chiang Mai, Thailand between 2010 and 2018. SaV was detected by RT-PCR and the polymerase and capsid gene sequences were analysed.

Results

From a total of 3,057 samples tested, 50 (1.6%) were positive for SaV. Among positive samples, SaV genotype GI.1 was the most predominant genotype (40%; 20/50), followed by GII.1 and GII.5 (each of 16%; 8/50), GI.2 (14%; 7/50), GIV.1 (4%; 2/50), and GI.5 (2%; 1/50). In addition, 4 SaV recombinant strains of GII.1/GII.4 were identified in this study (8%; 4/50).

Conclusions

The data revealed the genetic diversity of SaV circulating in children with AGE in Chiang Mai, Thailand during 2010 to 2018 and the intragenogroup SaV recombinant strains were reported for the first time in Thailand.

Clinical manifestation of norovirus infection in children aged less than five years old admitted with acute diarrhea in Surabaya, Indonesia: a cross-sectional study

Background: The objective of this study was to investigate the clinical manifestation of norovirus infection between norovirus genogroup and severity of acute diarrhea in pediatric patients at the Dr. Soetomo Hospital, Surabaya, Indonesia. Methods: This cross-sectional study involved 31 participants aged 1-60 months admitted to the hospital with acute diarrhea from April 2012 to March 2013. Norovirus genogroups (GI and II) were identified from patient stool using reverse transcription polymerase chain reaction (RT-PCR). Severity was measured using the Ruuska and Vesikari scoring system. Results: In total, 94 stool samples were obtained, of which 31 (19%) were norovirus positive. Norovirus GI was found in one sample with mild diarrhea. Norovirus GII was found in 30 samples (96.8%); one sample with mild diarrhea (3.3%), 20 samples with moderate diarrhea (66.7%), and nine samples with severe diarrhea (30%). Conclusion: Norovirus GII was the most prevalent cause of acute diarrhea and 30% of the cases manifested as severe diarrhea.

Molecular characterization of norovirus infection responsible for acute diarrhea in Congolese hospitalized children under five years old in Brazzaville, Republic of Congo

BACKGROUND

Acute diarrhea is a leading cause of morbidity and mortality among children under five worldwide. As no published data is available on the occurrence of this infection in the Republic of Congo, this study aimed at (1) determining the prevalence and (2) characterizing genotypes of norovirus strains in Brazzaville.

METHODS

From June 2012 to June 2013, stool samples were collected from hospitalized young children with acute gastroenteritis. A total of 545 samples were tested for GI and GII norovirus infections using nested duplex reverse-transcription-polymerase chain reaction and sequencing.

RESULTS

The GI and GII norovirus infection were detected in 148 samples. Males (28%) were not significantly more infected than females (25%). Norovirus infection was found exclusively in children aged under 24 months with a higher prevalence (P=0,048) in the age group of 7-12 months, and throughout the year with a peak in August and September. Genetic diversity of norovirus strains revealed that GII was the most prevalent (87%). No risk factor was significantly associated with norovirus infection.

CONCLUSION

This study showed that noroviruses are important agents responsible for acute diarrhea in Congolese children and highlights the importance of continued surveillance.

Norovirus Infections and Disease in Lower-MiddleandLow-Income Countries, 1997⁻2018

Noroviruses are a major cause of viral gastroenteritis. The burden of the norovirus in low-resource settings is not well-established due to limited data. This study reviews the norovirus prevalence, epidemiology, and genotype diversity in lower-middle-income countries (LMIC) and in low-income countries (LIC). PubMed was searched up to 14 January 2019 for norovirus studies from all LIC and LMIC (World Bank Classification). Studies that tested gastroenteritis cases and/or asymptomatic controls for norovirus by reverse transcription-polymerase chain reaction (RT-PCR) were included. Sixty-four studies, the majority on children <5 years of age, were identified, and 14% (95% confidence interval; CI 14–15, 5158/36,288) of the gastroenteritis patients and 8% (95% CI 7–9, 423/5310) of healthy controls tested positive for norovirus. In LMIC, norovirus was detected in 15% (95% CI 15–16) of cases and 8% (95% CI 8–10) of healthy controls. In LIC, 11% (95% CI 10–12) of symptomatic cases and 9% (95% CI 8–10) of asymptomatic controls were norovirus positive. Norovirus genogroup II predominated overall. GII.4 was the predominant genotype in all settings, followed by GII.3 and GII.6. The most prevalent GI strain was GI.3. Norovirus causes a significant amount of gastroenteritis in low-resource countries, albeit with high levels of asymptomatic infection in LIC and a high prevalence of coinfections.

Prevalence of Human Sapovirus in Low and Middle Income Countries

Background

Sapovirus (SV) infection is a public health concern which plays an important role in the burden of diarrhoeal diseases, causing acute gastroenteritis in people of all ages in both outbreaks and sporadic cases worldwide.

Objective/Study Design

The purpose of this report is to summarise the available data on the detection of human SV in low and middle income countries. A systematic search on PubMed and ScienceDirect database for SV studies published between 2004 and 2017 in low and middle income countries was done. Studies of SV in stool and water samples were part of the inclusion criteria.

Results

From 19 low and middle income countries, 45 published studies were identified. The prevalence rate for SV was 6.5%. A significant difference (P=0) in SV prevalent rate was observed between low income and middle income countries. Thirty-three (78.6%) of the studies reported on children and 8 (19%) studies reported on all age groups with diarrhoea. The majority (66.7%) of studies reported on hospitalised patients with acute gastroenteritis. Sapovirus GI was shown as the dominant genogroup, followed by SV-GII.

Conclusion

The detection of human SV in low and middle income countries is evident; however the reports on its prevalence are limited. There is therefore a need for systematic surveillance of the circulation of SV, and their role in diarrhoeal disease and outbreaks, especially in low and middle income countries.

Oyster Contamination with Human Noroviruses Impacted by Urban Drainage and Seasonal Flooding in Vietnam

This study investigated the level of norovirus contamination in oysters collected at a lagoon receiving urban drainage from Hue City for 17 months (August 2015-December 2016). We also investigated the genetic diversity of norovirus GI and GII in oyster and wastewater samples by using pyrosequencing to evaluate the effect of urban drainage on norovirus contamination of oysters. A total of 34 oyster samples were collected at two sampling sites (stations A and B) in a lagoon. Norovirus GI was more frequently detected than GII (positive rate 79 vs. 41%). Maximum concentrations of GI and GII were 2.4 × 10⁵ and 2.3 × 10⁴ copies/g, respectively. Co-contamination with GI and GII was observed in 35% of samples. Norovirus GII concentration was higher at station A in the flood season than in the dry season (P = 0.04, Wilcoxon signed-rank test). Six genotypes (GI.2, GI.3, GI.5, GII.2, GII.3, and GII.4) were identified in both wastewater and oyster samples, and genetically similar or identical sequences were obtained from the two types of samples. These observations suggest that urban drainage and seasonal flooding contribute to norovirus contamination of oysters in the study area.

Development of a quantitative real-time PCR assay for sapovirus in children under 5-years-old in Regina Margherita Hospital of Turin, Italy

Gastroenteritis is a common disease in children. It is characterized by diarrhea, vomiting, abdominal pain, and fever. Sapovirus (SaV) is a causative agent of acute gastroenteritis, but it causes milder illness than do rotavirus and norovirus. There is high variability in the analytical performance of quantitative PCR-based assays among clinical laboratories. This study developed a reverse transcription real-time PCR method to detect SaV in fecal specimens collected from children under 5-years-old with acute gastroenteritis. Of 137 episodes of acute gastroenteritis, 15 (10.9%) were associated with SaV genomic detection, with a median viral load of 6.6(log10) ± 7.1(log10) genomes/mg fecal specimens. There was a significant difference in detection rate between males and females (9.48% (13/15) vs. 1.46% (2/15), p = 0.0232). Among the 15 SaV-positive cases, 6 were also positive for rotavirus. Viral RNA recovery rate ranged from 46% to 77% in the manual RNAzol protocol and from 31% to 90% in the automated Maxwell protocol. We also studied whether human genomic DNA influences the sensitivity of the assay: its presence caused a decrease in PCR sensitivity. The development of a laboratory-designed real-time PCR TaqMan assay for quantitative detection of SaV and the optimization and standardization of this assay, using stools of children with acute gastroenteritis, are described.

Unbiased whole-genome deep sequencing of human and porcine stool samples reveals circulation of multiple groups of rotaviruses and a putative zoonotic infection

Coordinated and synchronous surveillance for zoonotic viruses in both human clinical cases and animal reservoirs provides an opportunity to identify interspecies virus movement. Rotavirus (RV) is an important cause of viral gastroenteritis in humans and animals. In this study, we document the RV diversity within co-located humans and animals sampled from the Mekong delta region of Vietnam using a primer-independent, agnostic, deep sequencing approach. A total of 296 stool samples (146 from diarrhoeal human patients and 150 from pigs living in the same geographical region) were directly sequenced, generating the genomic sequences of sixty human rotaviruses (all group A) and thirty-one porcine rotaviruses (thirteen group A, seven group B, six group C, and five group H). Phylogenetic analyses showed the co-circulation of multiple distinct RV group A (RVA) genotypes/strains, many of which were divergent from the strain components of licensed RVA vaccines, as well as considerable virus diversity in pigs including full genomes of rotaviruses in groups B, C, and H, none of which have been previously reported in Vietnam. Furthermore, the detection of an atypical RVA genotype constellation (G4-P[6]-I1-R1-C1-M1-A8-N1-T7-E1-H1) in a human patient and a pig from the same region provides some evidence for a zoonotic event.

Diverse sapovirus genotypes identified in children hospitalised with gastroenteritis in selected regions of South Africa

BACKGROUND

Sapoviruses (SaVs) are recognised as causative agents of gastroenteritis worldwide. However, data on the genetic diversity of this virus in Africa are lacking, particularly in the form of current long-term studies.

OBJECTIVE

To determine the genetic diversity of SaVs in children hospitalised with gastroenteritis in South Africa (SA).

STUDY DESIGN

From April 2009 to December 2013, SaVs were characterised from stool specimens from children hospitalised with gastroenteritis in four provinces of SA.

RESULTS

Fourteen different SaV genotypes were identified from the 221 strains that were characterised. Genogroup (G) IV predominated overall and was detected in 24% (53/221) of specimens. The other identified genotypes included six belonging to GI (GI.1-GI.3, GI.5, GI.6, and GI.7) and seven belonging to GII (GII.1-GII.7).

CONCLUSION

This study has provided the first comprehensive data on the genetic diversity of SaVs in a clinical setting in SA, contributing to the global knowledge of this virus.

Determination of cut-off cycle threshold values in routine RT-PCR assays to assist differential diagnosis of norovirus in children hospitalized for acute gastroenteritis

Norovirus (NV) is an important cause of acute gastroenteritis in children, but is also frequently detected in asymptomatic children, which complicates the interpretation of NV detection results in both the clinical setting and population prevalence studies. A total of 807 faecal samples from children aged <5 years hospitalized for acute gastroenteritis were collected in Thai Binh, Vietnam, from January 2011 to September 2012. Real-time RT-PCR was used to detect and quantify NV-RNA in clinical samples. A bimodal distribution of cycle threshold (Ct) values was observed in which the lower peak was assumed to represent cases for which NV was the causal agent of diarrhoea, whereas the higher peak was assumed to represent cases involving an alternative pathogen other than NV. Under these assumptions, we applied finite-mixture modelling to estimate a threshold of Ct <21·36 (95% confidence interval 20·29-22·46) to distinguish NV-positive patients for which NV was the likely cause of diarrhoea. We evaluated the validity of the threshold through comparisons with NV antigen ELISA results, and comparisons of Ct values in patients co-infected with rotavirus. We conclude that the use of an appropriate cut-off value in the interpretation of NV real-time RT-PCR results may improve differential diagnosis of enteric infections, and could contribute to improved estimates of the burden of NV disease.

Comprehensive review of human sapoviruses

Sapoviruses cause acute gastroenteritis in humans and animals. They belong to the genus Sapovirus within the family Caliciviridae. They infect and cause disease in humans of all ages, in both sporadic cases and outbreaks. The clinical symptoms of sapovirus gastroenteritis are indistinguishable from those caused by noroviruses, so laboratory diagnosis is essential to identify the pathogen. Sapoviruses are highly diverse genetically and antigenically. Currently, reverse transcription-PCR (RT-PCR) assays are widely used for sapovirus detection from clinical specimens due to their high sensitivity and broad reactivity as well as the lack of sensitive assays for antigen detection or cell culture systems for the detection of infectious viruses. Sapoviruses were first discovered in 1976 by electron microscopy in diarrheic samples of humans. To date, sapoviruses have also been detected from several animals: pigs, mink, dogs, sea lions, and bats. In this review, we focus on genomic and antigenic features, molecular typing/classification, detection methods, and clinical and epidemiological profiles of human sapoviruses.

Clinical epidemiology and molecular profiling of human bocavirus in faecal samples from children with diarrhoea in Guangzhou, China

To understand the clinical epidemiology and molecular characteristics of human bocavirus (HBoV) infection in children with diarrhoea in Guangzhou, South China, we collected 1128 faecal specimens from children with diarrhoea from July 2010 to December 2012. HBoV and five other major enteric viruses were examined using real-time polymerase chain reaction. Human rotavirus (HRV) was the most prevalent pathogen, detected in 250 (22·2%) cases, followed by enteric adenovirus (EADV) in 76 (6·7%) cases, human astrovirus (HAstV) in 38 (3·4%) cases, HBoV in 17 (1·5%) cases, sapovirus (SaV) in 14 (1·2%) cases, and norovirus (NoV) in 9 (0·8%) cases. Co-infections were identified in 3·7% of the study population and 23·5% of HBoV-positive specimens. Phylogenetic analysis revealed 14 HBoV strains to be clustered into species HBoV1 with only minor variations among them. Overall, the detection of HBoV appears to partially contribute to the overall detection gap for enteric infections, single HBoV infection rarely results in severe clinical outcomes, and HBoV sequencing data appears to support conserved genomes across strains identified in this study.

Association between norovirus and rotavirus infection and histo-blood group antigen types in Vietnamese children

Norovirus and rotavirus are the two most important causes of acute gastroenteritis in children worldwide. Both norovirus and rotavirus recognize human histo-blood group antigens (HBGAs), and multiple binding patterns for HBGAs have been reported. To explore the role of HBGAs in host susceptibility to norovirus and rotavirus, we conducted a cross-sectional study in children hospitalized with diarrhea in northern Vietnam from September 2010 through September 2012. Of 260 children with paired stool and saliva samples, 158 (61%) were classified as HBGA secretors (Lea-b+), 31 (12%) were nonsecretors (Lea+b-), and 71 (27%) were partial secretors (Lea+b+). Norovirus was detected in 50 patients (19%), with viral genotypes GII.3 (n=28) and GII.4 (n=22) being the most common. All children infected with norovirus strains of genotype GII.4 were either HBGA secretors or partial secretors. Of the 28 GII.3 cases, 12 involved HBGA secretors, 11 partial secretors, and 5 nonsecretors. A total of 85 children tested positive for rotavirus, 74 of whom were infected with genotype P[8], 5 with P[4], and 6 with P[6]; all were HBGA secretors or partial secretors. This is the first epidemiological study demonstrating in a population that HBGA phenotype is a key susceptibility factor for both norovirus and rotavirus infections in children.

Endemic norovirus infections in children, Ho Chi Minh City, Vietnam, 2009-2010

We performed a case–control investigation to identify risk factors for norovirus infections among children in Vietnam. Of samples from 1,419 children who had diarrhea and 609 who were asymptomatic, 20.6% and 2.8%, respectively, were norovirus positive. Risk factors included residential crowding and symptomatic contacts, indicating person-to-person transmission of norovirus.

Human caliciviruses detected in HIV-seropositive children in Kenya

The human caliciviruses (HuCVs) are important causes of gastroenteritis worldwide. Norovirus (NoV) and sapovirus (SaV) have been detected in HIV-seropositive children but the genetic diversity of HuCVs circulating in these individuals is largely unknown. In this study the prevalence and genotype diversity of HuCVs circulating in Kenyan HIV-positive children, with or without diarrhea, from the year 1999 to 2000 was investigated. The overall prevalence of HuCVs was 19% with NoV predominating at 17% (18/105) and SaV present in 5.7% (6/105) of specimens. Human CVs were detected in both symptomatic (24%) and asymptomatic (16%) children. Co-infections with other enteric viruses were detected in 21.6% of children with diarrhea but only in 4.4% of children without diarrhea. Remarkable genetic diversity was observed with 12 genotypes (7 NoV, 5 SaV) being identified in 20 HuCV-infected children. NoV genogroup II (GII) strains predominated with GII.2 and GII.4 each representing 27% of the NoV-positive strains. The GII.4 strain was most closely related to the nonepidemic GII.4 Kaiso 2003 variant. Other NoV genotypes detected were GI.3, GII.6, GII.12, GII.14, and GII.17. Five different SaV genotypes (GI.2, GI.6, GII.1, GII.2, and GII.4) were characterized from six specimens. Diarrheal symptoms were not associated with any specific HuCV genotype. Overall the HuCV genotype distribution detected in this study reflects those in other studies worldwide. The strains detected are closely related to genotypes that have circulated on several continents since the year 2000.

The dynamics of GII.4 Norovirus in Ho Chi Minh City, Vietnam

Norovirus (NoV) is a major cause of epidemic gastroenteritis in industrialized countries, yet the epidemiological significance of NoV in industrializing countries remains poorly understood. The spatiotemporal distribution of NoV genotypes identified in 2054 enrolled children was investigated between May 2009 and December 2010, in Ho Chi Minh City (HCMC), Vietnam. A total of 315 NoV extracted from stool samples were genotyped and GPS mapped to their source. Genogroup II NoV, particularly GII.4, were predominant, and the GII.4 strains could be subgrouped into GII.4-2006b (Minerva) and GII.4-2010 (New Orleans) variants. There was no spatiotemporal structure among the endemic GII strains; yet a significant spatiotemporal signal corresponding with the novel introduction of GII.4-2010 variant was detected. These data show that NoV GII.4 variants are highly endemic in HCMC and describe a scenario of rapid NoV strain replacement occurring in HCMC in early 2010.

Molecular epidemiology of noroviruses associated with acute sporadic gastroenteritis in children: global distribution of genogroups, genotypes and GII.4 variants

Noroviruses are a leading cause of epidemic and sporadic acute gastroenteritis worldwide. The development of sensitive molecular diagnostic techniques has revolutionized our understanding of norovirus epidemiology over the past two decades, but norovirus strain types associated with sporadic gastroenteritis remain poorly described. Therefore, we conducted a systematic review of studies performed after 2000 to clarify the genotypic distribution of noroviruses in children (≤18 years of age) with sporadic acute gastroenteritis. Genogroup GII norovirus was the most prevalent, accounting for 96% of all sporadic infections. GII.4 was the most prevalent genotype, accounting for 70% of the capsid genotypes and 60% of the polymerase genotypes, followed by the capsid genotype GII.3 (16%) and the polymerase genotype GII.b (14%). The most common ORF1/ORF2 inter-genotype recombinants were GII.b, GII.12, and GII.4 polymerase genotypes combined with the capsid genotype GII.3, accounting for 19% of all genotyped strains. The distribution of GII.4 variants over the last decade was dominated by successive circulation of GII.4/2002, GII.4/2004, GII.4/2006b, and GII.4/2008 with GII.4/2006b continuing to date. Genotypes GII.4 and GII.3 have predominated in children during the past decade; this is most notable in the global emergence of GII.4 variant noroviruses. As the burden of rotavirus disease decreases following the introduction of childhood immunization programs, the relative importance of norovirus in the etiology of acute childhood gastroenteritis will likely increase. In order for a successful norovirus vaccine to be developed, it should provide immunity against strains with capsid genotypes GII.4 and GII.3.