Characterization of astrovirus-associated gastroenteritis in hospitalized children under five years of age

Near-complete genome sequence of human astrovirus recovered from a child with acute flaccid paralysis in Guinea, 2021

Astroviruses are common causes of gastroenteritis in humans and other animals. Herein, we reported a near-complete human astrovirus (HAstV) sequence detected in a child with acute flaccid paralysis. The sample was collected in Guinea in January 2021. Phylogenetic analyses indicated that this virus belonged to the HAstV-1 genotype.

Worldwide prevalence and genotype distribution of human astrovirus in gastroenteritis patients: A systematic review and meta-analysis

AIM

Human astrovirus (HAstV) is an important causative agent of gastroenteritis in humans, which mainly infects young children and the elderly. The goal of this study was to conduct a meta-analytic review of the prevalence of HAstV amongst patients with gastroenteritis, and to shed light on the connection between HAstV infection and gastroenteritis.

METHODS

Systematic literature searches were conducted to identify all potentially relevant studies recorded up to April 8th, 2022. For study weighting, the inverse variance method was employed and the random-effects model was applied to evaluate data. For case-control studies, the pooled odds ratio (OR) and 95% confidence interval (CI) were calculated to establish the relationship between HAstV infection and gastroenteritis.

RESULTS

Among 302423 gastroenteritis patients from 69 different countries, the overall pooled prevalence of HAstV infection was 3.48% (95% CI: 3.11%-3.89%). Case-control approach was used in 39 investigations, and the overall prevalence of HAstV infection among the 11342 healthy controls was 2.01% (95% CI: 1.40%-2.89%). Gastroenteritis and HAstV infection were associated with a pooled OR of 2.16 (95% CI: 1.72-2.71; P < 0.0001; I² = 33.7%). The most commonly found HAstV genotypes in gastroenteritis patients were HAstV1 (62.18%), HAstV7 (33.33%), and HAstV-MLB1 (17.43%).

CONCLUSION

The frequency of HAstV infection was the highest in children under the age of five, and in developing countries. The prevalence rate of HAstV was not influenced by gender. Semi-nested and nested RT-PCR were highly sensitive assays for detecting HAstV infections.

Structure of the divergent human astrovirus MLB capsid spike

Despite their worldwide prevalence and association with human disease, the molecular bases of human astrovirus (HAstV) infection and evolution remain poorly characterized. Here, we report the structure of the capsid protein spike of the divergent HAstV MLB clade (HAstV MLB). While the structure shares a similar folding topology with that of classical-clade HAstV spikes, it is otherwise strikingly different. We find no evidence of a conserved receptor-binding site between the MLB and classical HAstV spikes, suggesting that MLB and classical HAstVs utilize different receptors for host-cell attachment. We provide evidence for this hypothesis using a novel HAstV infection competition assay. Comparisons of the HAstV MLB spike structure with structures predicted from its sequence reveal poor matches, but template-based predictions were surprisingly accurate relative to machine-learning-based predictions. Our data provide a foundation for understanding the mechanisms of infection by diverse HAstVs and can support structure determination in similarly unstudied systems.

Use of multiplex PCR in diagnosis of childhood acute viral diarrhoea caused by rotavirus, norovirus, astrovirus and adenovirus in Upper Egypt

Background

Diarrhoea is still a major public health issue in developing countries, and it is one of the leading causes of morbidity and mortality in children. We aimed to assess the use of a multiplex reverse transcription polymerase chain reaction (RT-PCR) assay for the detection of five viruses, including rotavirus, norovirus (genogroups 1 and 2), astrovirus, and adenovirus, responsible for gastroenteritis in children under 5 years old in primary care centres in Upper Egypt.

Subjects and methods

A total of 500 stool samples were collected. Fifty samples were randomly selected for viral examination using multiplex RT-PCR for the detection of rotavirus, norovirus (genogroups 1 and 2), astrovirus, and adenovirus, causing diarrhoea.

Results

Viruses were detected in 45 (90%) of the 50 stool samples. The most frequently identified virus was norovirus G2, followed by Group A rotavirus, astrovirus and adenovirus. Mixed infection by two and three viruses was observed in 7/50 cases (14%) and 2/50 cases (4%), respectively. Norovirus G1 was not detected in the samples examined.

Conclusion

Our study reveals that multiplex PCR allows for the detection of multiple viral targets in only one reaction, rendering the assay easier to perform compared to existing testing methodologies (RT-PCR and electron microscopy). Additionally, most of the viruses were detected in summer, and the highest prevalence was in the age group less than 1 year. Norovirus G2 and rotavirus were the most frequent agents and the most common coinfections responsible for gastroenteritis in children.

Detection and characterization of human astrovirus and sapovirus in outpatients with acute gastroenteritis in Guangzhou, China

Background

Human astrovirus (HAstV) and sapovirus (SaV) are common pathogens that can cause acute gastroenteritis (AGE). However, very few studies have reported the molecular epidemiology and clinical information on HAstV and SaV in China. This study aims to determine the molecular epidemiology and clinical features of HAstV and SaV in patients with AGE in Guangzhou, China.

Methods

For this study, 656 patients with AGE were enrolled. Their stool samples were screened for 15 enteropathogens using Luminex xTAG^® Gastrointestinal Pathogen Panel. HAstV and SaV were detected through an in-house multiplex reverse transcriptase polymerase chain reaction followed by phylogenetic analysis. We described and compared clinical features of AGE in patients with HAstV and SaV.

Results

Of the 656 stool samples, 63.72% (418/656) were found to be positive, with 550 enteropathogens (296 bacteria and 254 viruses). HAstV and SaV were detected in 20 (3.0%) and 12 (1.8%) samples, respectively. Four genotypes (genotypes 1, 2, 3, and 8) of HAstV and three genotypes (GI.1, GI.2 and GIV) of SaV were identified. Coinfection was observed in ten HAstV-positive and two SaV-positive samples. HAstV was more likely to occur in winter, while SaV in early spring. The median age of the patients with single HAstV infection was higher than that of the patients with other viruses (rotavirus, norovirus, and enteric adenovirus; P = 0.0476) and unknown etiology (P = 0.006). Coinfection with HAstV or SaV were not associated with disease severity (P > 0.05).

Conclusion

HAstV and SaV are the common causes of AGE in Guangzhou, China.

Human Astrovirus in Symptomatic and Asymptomatic Children: A Cross-Sectional Study on Hospitalized and Outpatients from Rural Communities of South Africa between 2017-2021

Human astroviruses are considered acute gastroenteritis agents (AGE) and are largely reported in children worldwide. There are limited data on astrovirus prevalence in rural communities, especially in hospitalized and asymptomatic cases. This study was a cross-sectional survey aiming to investigate the prevalence of classic human astroviruses in symptomatic and asymptomatic cases and hospitalized and outpatient children in rural communities of the Vhembe District, South Africa. A total of 236 stool samples (166 symptomatic and 70 asymptomatic) were collected from young children under 5 years of age. Real-time RT-PCR for astrovirus detection, RT-PCR amplification of capsid and polymerase partial genes as well as Sanger sequencing were performed. The classic astrovirus prevalence in symptomatic patients (7.23%, 12/166) as compared to healthy controls (4.29%, 3/70) was not statistically different (t-value: 1.782, p = 0.141: 95% CI). We did not observe a significant difference of classic astrovirus prevalence rate between the hospitalized group (6.52%, 3/46) and outpatient group (7.5%, 9/120). Symptomatic children below 6 months old were the most affected group (18.18%, 6/33). This study characterized human astrovirus genotype 2 and a putative recombinant strain (polymerase genotype 1/capsid genotype 2). Phylogenetic analysis revealed these genotypes are closely related to the strains circulating elsewhere within the African continent. The findings suggest that astrovirus is a common enteric pathogen in the study area. The results highlight the exposure of children and the need to monitor astroviruses for their potential impact in diarrhoeal diseases.

Molecular and epidemiological characterization of human adenovirus and classic human astrovirus in children with acute diarrhea in Shanghai, 2017-2018

BACKGROUND

In addition to rotavirus and norovirus, human adenovirus (HAdV) and classic human astrovirus (classic HAstV) are important pathogens of acute diarrhea in infants and young children. Here, we present the molecular epidemiology of HAdV and classic HAstV in children with acute diarrhea in Shanghai.

METHODS

Fecal specimens were collected from 804 outpatient infants and young children diagnosed with acute diarrhea in Shanghai from January 2017 to December 2018. All of the samples were screened for the presence of HAdV and classic HAstV. HAdV and classic HAstV were detected using traditional PCR and reverse-transcription PCR, respectively. All of the HAdV and classic HAstV positive samples were genotyped by phylogenetic analysis.

RESULTS

Among the 804 fecal samples, 8.58% (69/804) of samples were infected with either HAdV or classic HAstV, and five were co-infected with two diarrhea viruses. The overall detection rates of HAdV and classic HAstV were 3.47% (28/804) and 5.22% (42/804), respectively. Four subgroups (A, B, C, and F) and seven genotypes (HAdV-C1, -C2, -B3, -C5, -A31, -F40, and -F41) of HAdV were detected. Subgroup F had the highest constituent ratio at 64.29% (18/28), followed by non-enteric HAdV of subgroup C (21.43%, 6/28) and subgroup B 10.71% (3/28). HAdV-F41 (60.71%, 17/28) was the dominant genotype, followed by HAdV-C2 (14.29%, 4/28) and HAdV-B3 (10.71%, 3/28). Two genotypes of classic HAstV (HAstV-1 and HAstV-5) were identified in 42 samples during the study period; HAstV-1 (95.24%, 40/42) was the predominant genotype, and the other two strains were genotyped as HAstV-5. No significant differences were found between boys and girls in the detection rates of HAdV (P = 0.604) and classic HAstV (P = 0.275). Over half of the HAdV infections (82.14%, 23/28) and classic HAstV infections (66.67%, 28/42) occurred in children less than 36 months. Seasonal preferences of HAdV and classic HAstV infections were summer and winter, respectively. In this study, the common clinical symptoms of children with acute diarrhea were diarrhea, vomiting, fever and abdominal pain.

CONCLUSIONS

Our findings indicate that HAdV and classic HAstV play important roles in the pathogenesis of acute diarrhea in children in Shanghai. Systematic and long-term surveillance of HAdV and classic HAstV are needed to monitor their prevalence in children and prevent major outbreak.

Natural infection of free-ranging mandrills (Mandrillus sphinx) by enteroviruses and astroviruses in southern Gabon

Enteroviruses (Picornaviridae) and astroviruses (Astroviridae) cause various diseases in humans and animals, including in non-human primates (NHPs). Some enteroviruses and astroviruses detected in NHPs are genetically related to those infecting humans, indicating the occurrence of interspecies transmissions. In this study, we screened 200 fecal samples of 56 free-ranging mandrills (Mandrillus sphinx) by nested reverse transcription-PCR with primers targeting the VP1 and RdRp genes, to evaluate the diversity of enterovirus and astrovirus infection, respectively, and the associated zoonotic risk. Overall, ten samples from six mandrills were enterovirus-positive (5%), and three samples from three mandrills were astrovirus-positive (1.5%). This is the first evidence of astrovirus infection in mandrills. Phylogenetic analyses based on the VP1 sequences revealed that all ten enterovirus sequences were part of the species Enterovirus J, suggesting low zoonotic risk. Phylogenetic analysis of the three astrovirus sequences showed that they all belonged to the Mamastrovirus genus. Two astrovirus sequences were highly divergent from all human astrovirus sequences (63.4-73% nucleotide identity), while one sequence (AstV-5) suggested cross-species transmission from humans to mandrills. Additional studies are needed to better characterize the identified astroviruses and to confirm whether mandrills are host of astroviruses than can be transmitted to humans.

Molecular epidemiology of astrovirus in children with gastroenteritis in southwestern Nigeria

Human astrovirus (HAstV) is recognized as one of the major causative agents of acute gastroenteritis in children worldwide. Data on the genetic diversity of HAstV in Nigeria are limited. The aim of this study was to determine the prevalence and molecular epidemiology of classical HAstV in children under 5 years of age with acute gastroenteritis in Ogun State, Nigeria. Fecal samples (331) as well as socio-demographic and clinical data were collected across the three senatorial districts of the state from February 2015 to April 2017. One hundred seventy-five samples were randomly selected and analyzed for the presence of HAstV using RT-PCR. PCR amplicons from positive samples were sequenced, and phylogenetic analysis was done to determine genotypes and lineages. The overall prevalence rate was 19.4% (34), with the highest occurrence observed in 2015 (41.4%). Viral coinfections were detected in 13 cases (38.2%). HAstV infection occurred throughout the year and in all age groups, mainly in the age group of 0-12 months. There was significant association between prevalence rate and collection year; however, no association was observed with gender, age, symptoms or risk factors. HAstV-5 was the predominant genotype (76.5%) circulating throughout the study period, followed by HAstV-1 (23.5%), which circulated only in the first 2 years of the study. Phylogenetic analysis showed that all HAstV-5 strains detected belonged to the 5a lineage, while HAstV-1 strains were grouped into lineage 1b. This study, to the best of our knowledge, is the first comprehensive report on molecular characterization of classical HAstV among children with gastroenteritis in the country, and this will serve as baseline information for implementing appropriate infection control practices.

Novel Human Astroviruses: Prevalence and Association with Common Enteric Viruses in Undiagnosed Gastroenteritis Cases in Spain

A remarkable percentage of acute gastroenteritis cases remain etiologically undiagnosed. The aim of the study was to determine the prevalence of common and emerging enteric viruses, such as novel human astroviruses, among undiagnosed samples from children with acute gastroenteritis. Epidemiological studies for novel human astroviruses are still scarce. Stool samples collected over two consecutive winter seasons (2016–2017) from children with gastroenteritis in Spain, which were negative for bacteria, rotavirus, and adenovirus by routine diagnostics were screened by real-time RT-PCR assays for the presence of classical and novel astrovirus, rotavirus, norovirus GI and GII, sapovirus, and adenovirus. Overall, 220/384 stool samples (57.3%) were positive for at least one virus. Co-infections were identified in 21% of cases. Among a total of 315 viruses identified, adenovirus was the most prevalent (n = 103), followed by rotavirus (n = 51), sapovirus (n = 50), classical astrovirus (n = 43), novel astroviruses (n = 42), and norovirus (n = 26). Novel astroviruses were present in 13.3% of virus-positive cases. Most novel astroviruses were found in children <2-year-old (30/39 children, 77%, p = 0.01) and were found in co-infection (66%). Only classical astroviruses demonstrated significant differences in the Cq values during mono-infections compared to co-infections. In conclusion, common enteric viruses may be frequently found in children with undiagnosed gastroenteritis, indicating the need to implement more sensitive diagnostic methods. Novel astroviruses circulate in the community and could be the cause of gastroenteritis among young children.

Human Astrovirus MLB Replication In Vitro: Persistence in Extraintestinal Cell Lines

MLB astroviruses were identified 10 years ago in feces from children with gastroenteritis of unknown etiology and have been unexpectedly detected in severe cases of meningitis/encephalitis, febrile illness of unknown etiology, and respiratory syndromes. The aim of this study was to establish a cell culture system supporting MLB astrovirus replication. We used two clinical strains to infect several cell lines, an MLB1 strain from a gastroenteritis case, and an MLB2 strain associated with a neurologic infection. Efforts to propagate the viruses in the Caco-2 cell line were unsuccessful. In contrast, we identified two human nonintestinal cell lines, Huh-7 and A549, permissive for both genotypes. After serial passages in the Huh-7.5 cell line, the adapted strains were able to establish persistent infections in the Huh-7.5, Huh-7AI, and A549 cell lines, with high viral loads (up to 10 log₁₀ genome copies/ml) detected by quantitative reverse transcription-PCR (RT-qPCR) in the culture supernatant. Immunofluorescence assays demonstrated infection in about 10% of cells in persistently infected cultures. Electron microscopy revealed particles of 32 to 33 nm in diameter after negative staining of cell supernatants and capsid arrays in ultrathin sections with a particularly high production in Huh-7.5 cells. Interferon (IFN) expression by infected cells and effect of exogenous IFN varied depending on the type of infection and the cell line. The availability of a cell culture system to propagate MLB astroviruses represents a key step to better understand their replicative cycle, as well as a source of viruses to conduct a wide variety of basic virologic studies.IMPORTANCE MLB astroviruses are emerging viruses infecting humans. More studies are required to determine their exact epidemiology, but several reports have already identified them as the cause of unexpected clinical diseases, including severe neurologic diseases. Our study provides the first description of a cell culture system for the propagation of MLB astroviruses, enabling the study of their replicative cycle. Moreover, we demonstrated the unknown capacity of MLB astrovirus to establish persistent infections in cell culture. Whether these persistent infections are also established in vivo remains unknown, but the clinical consequences would be of high interest if persistence was confirmed in vivo Finally, our analysis of IFN expression provides some trails to understand the mechanism by which MLB astroviruses can cause persistent infections in the assayed cultures.

Molecular Epidemiology of Human Astrovirus in Stool Samples From Patients With Acute Gastroenteritis in Korea, 2013-2017

Background

Human astroviruses (HAstVs) are one of the major causes of acute gastroenteritis. Classic HAstVs can be classified into eight genotypes. We investigated the positive rate of HAstVs and the distribution of HAstV genotypes in strains isolated from patients with acute gastroenteritis in Hwaseong, Korea, in 2013–2017.

Methods

Between November 2013 and December 2017, 3,519 stool samples were collected from patients with symptoms of acute gastroenteritis and tested for HAstV using multiplex PCR. For HAstV-positive samples, the ORF2 gene, which encodes a capsid protein, was genotyped by reverse-transcription PCR and sequencing. Phylogenetic analysis was performed to determine whether the sequences of the HAstVs differed by year.

Results

The positive rate of HAstV was 1.9% (67 samples). HAstV Type 1 was the most prevalent genotype (82.4%), and Types 4, 5, and 8 were also detected. Infection occurred year-round, with no distinct seasonal variation. Infection occurred at nearly all ages (55 days–81 years; median: 3 years), and the positive rate was substantially higher in children younger than five years. Phylogenetic analysis revealed three distinct clades of HAstV Type 1 according to the collection time.

Conclusions

Our results provide recent epidemiological data on HAstVs in Korea between 2013 and 2017. The finding of three distinct clades of HAstV Type 1 according to collection time suggests genetic evolution of HAstVs. These findings can enhance our knowledge on HAstV infection and viral evolution.

Discovery of novel astrovirus and calicivirus identified in ruddy turnstones in Brazil

Birds are the natural reservoir of viruses with zoonotic potential, as well as contributing to the evolution, emergence, and dissemination of novel viruses. In this study, we applied a high-throughput screening approach to identify the diversity of viruses in 118 samples of birds captured between October 2006 to October 2010 in the North and Northeast regions of Brazil. We found nearly complete genomes of novel species of astrovirus and calicivirus in cloacal swabs of ruddy turnstones (Arenaria interpres) collected in Coroa do Avião islet, Pernambuco State. These viruses are positive-sense single-stranded RNA with a genome of ~7 to 8 kb, and were designated as Ruddy turnstone astrovirus (RtAstV) and Ruddy turnstone calicivirus (RTCV), respectively. Phylogenetic analysis showed that RtAstV and RTCV grouped in a monophyletic clade with viruses identified from poultry samples (i.e., chicken, goose, and turkey), including viruses associated with acute nephritis in chickens. Attempts of viral propagation in monkey and chicken cell lines for both viruses were unsuccessful. Also, we found genomes related with viral families that infect invertebrates and plants, suggesting that they might be ingested in the birds' diet. In sum, these findings shed new light on the diversity of viruses in migratory birds with the notable characterization of a novel astrovirus and calicivirus.

Complete Genome Sequences of Human Astrovirus Prototype Strains (Types 1 to 8)

We report the complete genome sequences of the eight human astrovirus Oxford prototype strains. These sequences share 94.9% to 99.9% nucleotide identity with open reading frame 2 (ORF2) genes of astrovirus genomes previously deposited in GenBank and include the first complete genome of human astrovirus type 7.

We report the complete genome sequences of the eight human astrovirus Oxford prototype strains. These sequences share 94.9% to 99.9% nucleotide identity with open reading frame 2 (ORF2) genes of astrovirus genomes previously deposited in GenBank and include the first complete genome of human astrovirus type 7.

Epidemiology of enteric viruses in children with gastroenteritis in Ogun State, Nigeria

Acute gastroenteritis (AGE) remains a global public health concern and Nigeria is one of the two countries accounting for 42% of global under-5 deaths attributable to gastroenteritis. This study aimed to determine the prevalence, seasonality, and risk factors of enteric viruses (EVs) in children with AGE in Ogun State, Nigeria. Stool samples collected from children under-5 from three different hospitals between February 2015 and April 2017 were analyzed using molecular methods for the presence of four EVs (group A rotavirus [RVA], norovirus [NoV], human astrovirus [HAstV], and human adenovirus [HAdV]). Among the 175 samples analyzed, 63 (36%) were positive for at least one EV. The most prevalent was HAstV (19.4%), followed by RVA (16.6%), NoV (5.1%), and HAdV (5.1%). Mixed infections were found in 17 cases. No significant association was observed with age, sex, and risk factors. Though not significant, EV prevalence was higher in the dry season. Positive cases (asides HAdV) had no correlation with temperature and/or humidity. This study provides information on the prevalence and seasonal fluctuations of EVs, which will be of value in the effective management of patients and control strategies for viral gastroenteritis in the country.

Molecular characterization of feline astrovirus in domestic cats from Northeast China

Feline astrovirus (FeAstV) which belonged to the genus Mamastrovirus was first identified in the feces of kittens with diarrhea in the USA in 1981 by electron microscopy, and had been reported in many countries. Presently, there are no any reports of the circulation of FeAstV in mainland China. We performed this study to investigate the apparent prevalence and genetic variability of FeAstV infected in cats in mainland China for the first time. We tested fecal samples of 105 cats with diarrhea and 92 asymptomatic cats in five cities in northeast China by RT-PCR targeting RNA-dependent RNA polymerase (RdRp) gene of FeAstV, and analyzed sequences variability and phylogenetic evolution based on the complete capsid gene of FeAstV strains obtained from positive samples. The overall prevalence of FeAstV was 23.4% (46/197) of which 38 were tested in cats with diarrhea (36.2%, 38/105) and 8 were in asymptomatic cats (8.7%, 8/92). Mixed infection with other enteroviruses including feline parvovirus (FPV), feline bocavirus (FBoV) and feline kobuvirus (FeKoV) was found in 38 FeAstV-positive samples. Phylogenetic analysis based on the complete capsid gene revealed all FeAstV strains were divided into two different groups with a 0.454±0.016 of mean amino acid genetic distance between two groups, suggesting that FeAstVs should be classified into two different genotype species. This study provided the first molecular evidence that FeAstV with considerable genetic diversity was circulating in northeast China, and analyzed genetic variability and classification of FeAstVs for the first time.

Molecular epidemiology of classic, MLB and VA astroviruses isolated from <5 year-old children with gastroenteritis in Thailand, 2011-2016

This study aimed to investigate the molecular epidemiology and genetic diversity of astrovirus circulating in pediatric patients with acute gastroenteritis in Thailand. A total of 2034 fecal specimens collected between 2011 and 2016 from children hospitalized with acute gastroenteritis were analyzed for astrovirus infection using RT-PCR and nucleotide sequencing techniques. Overall, 54 samples were positive for astrovirus (2.6%). About half of the virus-positive samples (57.4%) were co-infection cases, mainly with rotavirus or norovirus. Genotyping revealed that three major clades, classic human astrovirus (HAstV) and newly emerging MLB and VA astroviruses co-circulated in the study population. At least seven different genotypes were identified and HAstV1 was the most predominant genotype detected (50%), followed by MLB1 (16.7%), HAstV4 (11.1%), HAstV5 and HAstV8 (7.4% each), MLB2 and VA2 (3.7% each). This study provided a useful information and contributed to molecular epidemiology of astroviruses including the novel MLB and VA astoviruses have been characterized and reported for the first time in Thailand.

Molecular detection of human enteric viruses circulating among children with acute gastroenteritis in Valencia, Venezuela, before rotavirus vaccine implementation

Background

The role of rotavirus as main etiologic agent of diarrhea has been well documented worldwide, including in Venezuela. However, information about the prevalence of gastrointestinal viruses such as calicivirus, adenovirus and astrovirus is limited and the contribution of other agents as Aichi virus and klassevirus is largely unknown. To explore the etiological spectrum of diarrhea associated with agents other than rotaviruses, 227 stool samples from children under 5 years old with acute gastroenteritis, collected in Valencia (Venezuela) from 2001 to 2005, and previously tested as rotavirus-negative, were analyzed for caliciviruses, adenoviruses, astroviruses, Aichi viruses, klasseviruses, picobirnaviruses and enteroviruses by specific RT-PCRs.

Results

At least one viral agent was detected in 134 (59%) of the samples analyzed, mainly from children under 24 months of age and most of them belonging to the lowest socioeconomic status. Overall, enterovirus was identified as the most common viral agent (37.9%), followed by calicivirus (23.3%), adenovirus (11.5%), astrovirus (3.5%), klassevirus (1.3%) and Aichi virus (0.4%), while no picobirnavirus was detected. Klasseviruses were found during 2004 and 2005 and Aichi viruses only in 2005, indicating their circulation in Venezuela; meanwhile, the rest of the viruses were detected during the whole study period. Coinfections with two or more viruses were found in 39 (29.1%) of the infected children, most under 24 months of age. Adenovirus was involved as the coinfecting agent in at least 46.9% of the cases, but no differences concerning socio-demographic variables were observed between the coinfected and the single infected children.

Conclusions

The results show that various enteric viruses, including enteroviruses, caliciviruses and adenoviruses, accounted for a significant proportion of infantile diarrhea cases in Venezuela before rotavirus vaccine implementation. In addition, emerging viruses as Aichi virus and klassevirus were found, indicating the need to continue monitoring their spreading into the communities. Efforts are needed to develop more accurate methods to identify the major causes of diarrhea and to provide tools for more effective preventive measures.