Genomic diversity of "Norwalk like viruses" (NLVs): pediatric infections in a Brazilian shantytown

Scientific Opinion on an update on the present knowledge on the occurrence and control of foodborne viruses

A review of the biology, epidemiology, diagnosis and public health importance of foodborne viruses was performed. Data needs to support a risk assessment were also identified. In addition possible control options and their anticipated impact to prevent or reduce the number of foodborne viral human infections were identified, including the scientific reasons for and against the establishment of food safety criteria and process hygiene criteria for viruses for certain food categories. Food may be contaminated by virus during all stages of the food supply chain, and transmission can occur by consumption of food contaminated during the production process (primary production, or during further processing), or contaminated by infected food handlers. Transmission of zoonotic viruses (e.g. HEV) can also occur by consumption of products of animal origin. Viruses do not multiply in foods, but may persist for extended periods of time as infectious particles in the environment, or in foods. At the EU-level it is unknown how much viral disease can be attributed to foodborne spread. The relative contribution of different sources (shellfish, fresh produce, food handler including asymptomatic shedders, food handling environment) to foodborne illness has not been determined. The Panel recommends focusing controls on preventive measures to avoid viral contamination rather than trying to remove/inactivate these viruses from food. Also, it is recommended to introduce a microbiological criteria for viruses in bivalve molluscs, unless they are labelled "to be cooked before consumption". The criteria could be used by food business operators to validate their control options. Furthermore, it is recommended to refine the regulatory standards and monitoring approaches in order to improve public health protection. Introduction of virus microbiological criteria for classification of bivalve molluscs production areas should be considered. A virus monitoring programme for compliance with these criteria should be risk based according to the findings of a sanitary survey.

Surveillance of norovirus infections in the state of Rio De Janeiro, Brazil 2005-2008

A 4-year (2005-2008) norovirus (NoV) surveillance study was conducted in the state of Rio Janeiro, Brazil, to demonstrate the role of these viruses in outbreaks and sporadic cases of acute gastroenteritis. A cohort of 1,687 fecal samples was obtained from patients with gastroenteritis; 324 were rotavirus-positive. Of the remainder 1,363 rotavirus-negative samples, 1,087 samples were tested for NoV RNA in this study. The study enrolled 267 outpatients from Municipal Public Health Centers and 820 inpatients, whose samples were obtained by active surveillance in Public Hospitals. Fecal samples were tested by reverse transcription (RT) followed by polymerase chain reaction (PCR) using the MON 431-434 set of degenerate primers for NoV GI and GII detection, and there were 35.1% (381/1,087) positive samples for NoV, consisting of 30.2% (248/820) and 49.8% (133/267) from inpatient and outpatient, respectively. Children infected by NoV had significantly more frequent mucus in feces, vomiting and fever. No seasonal pattern in NoV infections was observed in patients admitted to hospital; however, two peaks of NoV infections were observed from ambulatory cases, suggesting that there was an occurrence of outbreaks in those time periods. Molecular characterization revealed GII to be the most prevalent genogroup, totaling 96.3% (104/108) of all sequences analyzed, and GII.4 was the genotype detected most frequently (80.7%), followed by GII.6, 3, 14, 7, and 8. Two GI strains, GI.2 and GI.3, were also observed. The number of outbreaks and sporadic cases described in this study highlights the need to implement diagnosis of NoV in surveillance laboratories.

Identification and molecular characterization of norovirus in são paulo state, Brazil

Norovirus (NoV), previously called Norwalk-like virus, represents an important group of human pathogens associated with outbreaks of nonbacterial gastroenteritis. Epidemiological surveys of outbreaks have shown that the most important routes of transmission are person-to-person contacts and contaminated food and water, with the virus affecting adults and children. NoV is classified into genogroups, being genogroups GI, GII and GIV found in humans. In view of the high genetic diversity of NoV and the lack of information about this virus in Brazil, the aim of the present study was the molecular characterization of NoV isolated from diarrheic stool samples of patients from São Paulo State. In this study, 204 stool specimens collected during diarrhea outbreaks were analyzed by RT-PCR, and 12 were sequenced for genogroup confirmation. One-step PCR was performed in order to amplify the B region of ORF 1 using the MON 431, 432, 433 and 434 primer pool. From total, 32 (15.7%) stool specimens were positive for NoV genogroup GII. Comparison of the sequences of the PCR products to GenBank sequences showed 88.8% to 98.8% identity, suggesting the presence of genogroup GII in gastroenteritis outbreaks in São Paulo State.

Immunology of Norovirus Infection

Noroviruses are the leading cause of epidemic non-bacterial gastroenteritis worldwide. Despite their discovery over three decades ago, little is known about the host immune response to norovirus infection. The purpose of this chapter is to review the field of norovirus immunology and discuss the contributions of outbreak investigations, human and animal challenge studies and population-based studies. This chapter will survey both humoral and cellular immunity as well as recent advances in norovirus vaccine development.

Intranasal administration of a recombinant adenovirus expressing the norovirus capsid protein stimulates specific humoral, mucosal, and cellular immune responses in mice

Norovirus (NV) is a major cause of acute, epidemic nonbacterial gastroenteritis in individuals of all ages. The immunological mechanism of NV infection and the approaches used to prevent infection remain to be elucidated. In this study, the specific immune responses of BALB/c mice were assessed following intranasal immunization with a recombinant adenovirus vector expressing the genogroup II4 (GGII/4) norovirus capsid protein. Analysis of IgM, IgG, and IgA antibodies specific for the recombinant virus-like particles (VLPs) of NV demonstrated that a high level of humoral immunity developed following immunization. Mucosal immune responses were also detectable in stool, intestinal homogenates, lung homogenates, and lung lavage samples. Specific cellular immune responses were observed in NV VLPs-restimulated splenocytes by ELISPOT and Th1/Th2 cytokine cytometric array (CBA). Serum IgG subclass analysis showed that a balanced Th1- and Th2-like cellular immune response was induced in BALB/c mice following immunization with recombinant adenovirus. These findings demonstrate that the intranasal immunization of a recombinant adenovirus expressing the NV capsid protein is an efficient strategy to stimulate systemic, mucosal, and cellular Th1/Th2 immune responses in mice, and could serve as a novel approach for designing NV vaccines.

Global impact of diarrheal diseases that are sampled by travelers: the rest of the hippopotamus

Travelers who experience diarrhea (i.e., "turista") are exposed to the same pathogens and illnesses that pose some of the greatest threats to life and development among malnourished children in developing areas around the world, where inadequate water and poor sanitation remain. This article focuses on new findings about the impact, diagnosis, and control of these illnesses and the genetic predispositions of persons who acquire them. Despite the reductions in mortality due to dehydrating diarrhea, the morbidity associated with diarrheal illnesses continues unabated. Furthermore, we increasingly recognize the lasting detrimental effects of enteric infections that occur during early childhood on later physical and cognitive development and, in patients with acquired immunodeficiency syndrome, on the absorption of antiretroviral drugs. Genetic predispositions to inflammation and potential protection associated with such alleles as ApoE4, which are not suspected of being involved in diarrhea, remind us of how much we have to learn about the effect and interactions of enteric tropical infectious diseases with regard to our host genome. New diagnostic methods hold promise for improved recognition and, hopefully, control of enteric infections worldwide.

Genetic diversity of norovirus among children with gastroenteritis in São Paulo State, Brazil

Norovirus (NoV) is one of the most common causes of acute gastroenteritis in children and adults. To study the prevalence and genetic variability of NoV in children with acute gastroenteritis in São Paulo State, Brazil, we examined 234 stool samples from children with or without gastroenteritis during a 5-year period (1995 to 1999). NoV RNA was detected by reverse transcription-PCR and confirmed by DNA sequence analysis. We used two different oligonucleotide primer sets targeting the 3' end of the RNA polymerase gene (region B), as well a partial capsid region at the 3' end of the VP1 gene (region D). A total of 78 (33.3%) of the samples tested positive for NoV, and in region B, of the 66 strains sequenced, 4 (6.1%) belonged to GI, 52 (78.7%) belonged to GII, and five samples (7.6%) contained a mixture of the GI and GII genotypes. Phylogenetic analysis showed that the majority (40 of 66 [60.6%]) of the strains belonged to genotype GII.4. The nucleotide sequence identity of three strains was lower than 77.9% compared to a region B reference sequence database but showed 85.3 to 88.8% identity with GII.2 Melksham strain in region D, indicating the circulation of a possible recombinant NoV strain. One sample (GII.3) was sequenced only in region D. In conclusion, we have a total of 67 sequenced strains. This is the first report that describes the predominance of GII.4 NoV strains in children visiting the ambulatory of different hospitals in São Paulo State, Brazil, and we show that mixtures of different strains can be found in individual samples, including some possible new recombinant strains.

Detection of calicivirus from fecal samples from children with acute gastroenteritis in the West Central region of Brazil

The objective of this study was to describe the circulation of caliciviruses in the West Central region of Brazil and its correlation with children's gender and age, as well as with the year and months of the sample collection. Reverse transcriptase-polymerase chain reaction was performed to detect the human calicivirus genome in 1006 fecal samples that were collected in Goiânia (n = 696) and Brasília (n = 310). Viral RNA was detected in 8.6% of the samples. No significant difference in viral prevalence was found regarding gender, age or year of the sample. However, it was observed that in Goiânia, there is a higher incidence of caliciviruses from September to March. The analysis employing three primer pairs demonstrated that the Ni/E3 or JV12/13 primer pairs, which detect norovirus (NoV), detected 41 positive samples while the 289/290 primer pair, which detects NoV or sapovirus, detected the remaining 46 samples. Calicivirus circulates in the West Central region of Brazil and for better detection of this virus it is important to use more than one primer pair. Also, we conclude that the seasonality presented by this virus is related to higher humidity in the period.

Molecular epidemiology of norovirus gastroenteritis outbreaks in North Carolina, United States: 1995–2000

Noroviruses (NoVs) are the most common cause of acute non-bacterial gastroenteritis outbreaks in the US. We investigated 16 gastroenteritis outbreaks in North Carolina (NC), from 1995 to 2000, to further characterize the epidemiology of NoV using RT-PCR on stool and ELISA on sera. NoV were identified in 14 outbreaks by RT-PCR. Sequence analyses of the amplicons indicated the outbreak strains belonged to the following clusters: five GII/4, three GI/3, one GI/4, one GII/2, one GII/5, one GII/7, and one GII/13 (prototype strain). We detected NoV in stool samples from one outbreak but could not determine its specific cluster within the GII genogroup based on polymerase sequence analysis. The five GII/4 strains were classified as the "95/96 US common strain" and occurred throughout the 5-year period. In contrast to national trends, the majority (86%) of NoV outbreaks identified in North Carolina were foodborne. Of the 12 food-related NoV outbreaks, we were able to document transmission by food handlers in two outbreaks. Person-to-person transmission from primary cases was suggested in three outbreaks. Our results indicate that NoVs are important agents of viral gastroenteritis outbreaks in NC.

Molecular epidemiology of norovirus infections in sporadic cases of viral gastroenteritis among children in Northern Italy

Surveillance of norovirus infections in sporadic cases of pediatric gastroenteritis admitted to a main hospital in Northern Italy during a full-year period (2002) showed that noroviruses (10.4%) were the second most common causative viral agent, following rotaviruses (21.1%), and noroviruses (81%) were mostly implicated in mixed infections. The epidemic period of norovirus was September-December, with September and November as months of major prevalence (33.3 and 38.5%, respectively). Six distinct norovirus genotypes were detected (GI.7, GII.1, GII.2, GII.4, GII.7, GII, not assigned named GIIb), and the predominant genotype was GII.4. A "new GII.4 2002 variant" accounted for 82.9% of total strains. Since the severity of norovirus symptoms does not usually require admission to hospital, the burden of norovirus disease in the general children population may be much higher than that suggested by the present hospital-based investigation.

A 5-year study of the prevalence and genetic diversity of human caliciviruses associated with sporadic cases of acute gastroenteritis in young children admitted to hospital in Melbourne, Australia (1998-2002)

The prevalence and genetic diversity of human caliciviruses causing sporadic cases of acute gastroenteritis in young children hospitalized in a large pediatric hospital in Melbourne, Australia over 5 years (incorporating January 1998-December 2002) was studied by reverse transcription and sequence analysis of part of the polymerase gene. The overall prevalence of calicivirus infection in children aged <5 years during the 5 year study was 9.2% (113/1,233), with 95% of the strains belonging to the Norovirus genera. Strains of the norovirus G11-4 cluster were the most common type identified in 4 of the 5 years studied (1998, 1999, 2001, and 2002), with strains of norovirus cluster G11-5 the most common type during 2000. Additional norovirus genetic clusters GI-3, GII-1, GII-2, GII-3, GII-6, and GII-7, were also identified, but comprised only 17/94 of norovirus genogroup II strains. Five sapovirus strains were also identified. These results highlight the divergence of norovirus strains identified in a pediatric population.

Broadly reactive nested reverse transcription-PCR using an internal RNA standard control for detection of noroviruses in stool samples

We developed a nested reverse transcription-PCR (nRT-PCR) for the detection of noroviruses in stools, using random primers for RT, the JV12/JV13 primer pair in the first round of nPCR, and a set of nine inner primers for the second, comprising the reverse sequences of primers SR46, SR48, SR50, and SR52, and five novel oligonucleotide sequences (113-1, 113-2, 115-1, 115-2, and 115-3). The specificity of the nRT-PCR was confirmed by testing 61 stools containing enteric viruses other than noroviruses. In comparative assays on either stools or RNA dilutions from two genogroup I and three genogroup II (GII) norovirus-positive samples, nRT-PCR was always at least as sensitive as RT-PCR and Southern hybridization. With some of the samples tested, the increase in sensitivity was 10-fold or higher. For GII viruses, the detectable range of nRT-PCR was estimated to be 8.4 x 10(4) to 2 RNA viral particles. When used on 85 stools from pediatric patients with acute gastroenteritis negative for viruses by electron microscopy and cell culture, the nRT-PCR detected norovirus in 19 samples (22.3%), while it failed to detect one reference RT-PCR-positive sample containing a Desert Shield strain. Sixteen of the 19 nRT-PCR-positive samples gave concordant results with reference RT-PCR and Southern hybridization, and all with sequence analysis. Partial sequencing of the polymerase region revealed that from January to April 2000 all GII strains except two (Rotterdam- and Leeds-like viruses) formed a tight cluster related to Hawaii virus. The nRT-PCR described could prove suitable for large epidemiological studies and for specialized clinical laboratories performing routine molecular testing.

Evaluation and validation of real-time reverse transcription-pcr assay using the LightCycler system for detection and quantitation of norovirus

We developed an assay for the detection and quantitation of norovirus with the LightCycler SYBR Green-based real-time reverse transcription-PCR (real-time LC RT-PCR) and previously published primers in the capsid and the polymerase gene. One hundred thirty-two stool specimens from the Provincial Laboratory for Public Health (Microbiology), Alberta, Canada, and the Centers for Disease Control and Prevention, Atlanta, Ga., were used to validate the new assay. The samples were collected from patients involved in outbreaks of acute gastroenteritis or children who presented with sporadic gastroenteritis. The real-time LC RT-PCR assay detected norovirus strains from three genogroup I (G-I) clusters (G-I/1, G-I/2, and G-I/3) and 10 genogroup II (G-II) clusters (G-II/1, G-II/2, G-II/3, G-II/4, G-II/6, G-II/7, G-II/10, G-II/12, G-II/15, and G-II/16). There was 100% concordance with the results from 58 stool specimens which tested positive by conventional RT-PCR assays. By dilution analysis, the real-time LC RT-PCR was 10,000 times more sensitive than the conventional RT-PCR. The new assay increased the number of samples in which noroviruses were detected by 19%. The real-time LC RT-PCR had a wide dynamic range, detecting from 5 to 5 x 10(6) copies of RNA per reaction, resulting in a theoretical lower limit of detection of 25,000 copies of RNA per g of stool. No cross-reactions were found with specimens containing sapovirus, rotavirus, astrovirus, and adenovirus. Because of the high sensitivity and specificity of the assay with a relatively rapid and simple procedure, the real-time LC RT-PCR will be useful as a routine assay for the clinical diagnosis of norovirus infection.

Diversity of enteric viruses detected in patients with gastroenteritis in a tertiary referral paediatric hospital

The genetic diversity of enteric viruses co-circulating in a cohort of patients with viral gastroenteritis in a large tertiary paediatric hospital in London, UK, was determined. Multiple strains of noroviruses (NV), sapoviruses (SV) and astroviruses (HAsV) were detected in these patients, indicating the likelihood of multiple introductions from different sources, possible sub-clinical infections and simultaneous infection with different viruses in immunocompromised and other patients. Routine screening of immunocompromised patients and infection control procedures are important to prevent nosocomial infection.

Noroviruses associated with acute gastroenteritis in a children's day care facility in Rio de Janeiro, Brazil

Noroviruses (Norwalk-like viruses) are an important cause of gastroenteritis worldwide. They are the most common cause of outbreaks of gastroenteritis in the adult population and occur in nursing homes for the elderly, geriatric wards, medical wards, and in hotel and restaurant settings. Food-borne outbreaks have also occurred following consumption of contaminated oysters. This study describes the application of a reverse transcription-polymerase chain reaction (RT-PCR) assay using random primers (PdN6) and specific Ni and E3 primers, directed at a small region of the RNA-dependent RNA polymerase-coding region of the norovirus genome, and DNA sequencing for the detection and preliminary characterisation of noroviruses in outbreaks of gastroenteritis in children in Brazil. The outbreak samples were collected from children <5 years of age at the Bertha Lutz children's day care facility at Oswaldo Cruz Foundation (Fiocruz), Rio de Janeiro, that occurred between 1996 and 1998, where no pathogen had been identified. At the Bertha Lutz day care center facility, only Fiocruz's employee children are provided for, and they come from different social, economic and cultural backgrounds. Three distinct genogroup II strains were detected in three outbreaks in 1997/98 and were most closely related to genotypes GII-3 (Mexico virus) and GII-4 (Grimsby virus), both of which have been detected in paediatric and adult outbreaks of gastroenteritis worldwide.

Incidence and characteristics of endemic Norwalk-like virus-associated gastroenteritis

Endemic gastroenteritis associated with the Norwalk-like viruses (NLVs) is little understood. This study tested for NLV in gastroenteritis cases in 257 households in Melbourne, Australia, for the period September 1997 to February 1999 by a reverse transcription hemi-nested polymerase chain reaction. Positive samples were studied by nucleotide sequencing and phylogenetic analysis. NLV was detected in 73 (11.4%) of 638 faecal specimens tested. Twelve (1.9%) were NLV genogroup 1 (G1) and 61 (9.6%) NLV genogroup 2 (G2). Gastroenteritis symptoms associated with NLV G2/no other pathogens were significantly more severe than where no NLV was detected. NLV G1 and NLV G2 were detected in adults and children, males and females. NLV G2 incidence showed a marked seasonal periodicity with significant peaks in the Australian late spring/early summer periods. NLV G1 seasonality was significantly different from that of NLV G2. Seven major NLV clusters were identified by phylogenetic analysis.

Evaluation of the NucliSens Basic Kit assay for detection of Norwalk virus RNA in stool specimens

Norwalk-like viruses (NLVs) are a genetically diverse group of human caliciviruses that are the most common cause of epidemic gastroenteritis and are detected typically in stool by reverse transcription (RT)-PCR or electron microscopy (EM). The application of a rapid nucleic acid sequence-based amplification (NASBA) assay for the detection of NLV RNA in stool is described using the NucliSens Basic Kit. Primers and probes for the NLV Basic Kit assay were based on the RNA polymerase region of the prototype NLV, Norwalk virus (NV) genome and could consistently detect 10(4) RT-PCR detectable units of NV RNA in a stool filtrate. When compared directly with RT-PCR on a dilution series of NV stool filtrate, the NucliSens Basic Kit assay was equally sensitive. Cross-reactivity studies with a representative panel of other enteric pathogens were negative. When applied to 15 stool specimens from NV-challenged volunteers, the NASBA Basic Kit application for NV detection yielded 100% sensitivity, 50% specificity, and 67% concordance, using RT-PCR as the 'gold standard'. Despite the specificity of the NASBA primer/probe sequences for NV, other representatives from both NLV genogroups I and II could be detected by the Basic Kit assay in outbreak stool specimens, although the results were inconsistent. Our results suggest that the NucliSens Basic Kit assay provides a rapid and sensitive alternative to RT-PCR for detecting NV RNA in stool specimens. However, improvements in test specificity and primer design will be needed before the assay can be used routinely in the clinical setting.

Foodborne viruses

Foodborne and waterborne viral infections are increasingly recognized as causes of illness in humans. This increase is partly explained by changes in food processing and consumption patterns that lead to the worldwide availability of high-risk food. As a result, vast outbreaks may occur due to contamination of food by a single foodhandler or at a single source. Although there are numerous fecal-orally transmitted viruses, most reports of foodborne transmission describe infections with Norwalk-like caliciviruses (NLV) and hepatitis A virus (HAV), suggesting that these viruses are associated with the greatest risk of foodborne transmission. NLV and HAV can be transmitted from person to person, or indirectly via food, water, or fomites contaminated with virus-containing feces or vomit. People can be infected without showing symptoms. The high frequency of secondary cases of NLV illness and - to a lesser extent - of hepatitis A following a foodborne outbreak results in amplification of the problem. The burden of illness is highest in the elderly, and therefore is likely to increase due to the aging population. For HAV, the burden of illness may increase following hygienic control measures, due to a decreasing population of naturally immune individuals and a concurrent increase in the population at risk. Recent advances in the research of NLV and HAV have led to the development of molecular methods which can be used for molecular tracing of virus strains. These methods can be and have been used for the detection of common source outbreaks. While traditionally certain foods have been implicated in virus outbreaks, it is clear that almost any food item can be involved, provided it has been handled by an infected person. There are no established methods for detection of viruses in foods other than shellfish. Little information is available on disinfection and preventive measures specifically for these viruses. Studies addressing this issue are hampered by the lack of culture systems. As currently available routine monitoring systems exclusively focus on bacterial pathogens, efforts should be made to combine epidemiological and virological information for a combined laboratory-based rapid detection system for foodborne viruses. With better surveillance, including typing information, outbreaks of foodborne infections could be reported faster to prevent further spread.

Expression and self-assembly of norwalk virus capsid protein from venezuelan equine encephalitis virus replicons

The Norwalk virus (NV) capsid protein was expressed using Venezuelan equine encephalitis virus replicon particles (VRP-NV1). VRP-NV1 infection resulted in large numbers of recombinant NV-like particles that were primarily cell associated and were indistinguishable from NV particles produced from baculoviruses. Mutations located in the N-terminal and P1 domains of the NV capsid protein ablated capsid self-assembly in mammalian cells.

Systemic, mucosal, and heterotypic immune induction in mice inoculated with Venezuelan equine encephalitis replicons expressing Norwalk virus-like particles

Norwalk-like viruses (NLVs) are a diverse group of single-stranded, nonenveloped, positive-polarity RNA viruses and are the leading cause of epidemic acute gastroenteritis in the United States. In this study, the major capsid gene of Norwalk virus, the prototype NLV, has been cloned and expressed in mammalian cells using a Venezuelan equine encephalitis (VEE) replicon expression system. Upon infection of baby hamster kidney (BHK) cells with VEE replicon particles (VRPs), the Norwalk virus capsid proteins self-assemble to generate high titers of Norwalk virus-like particles (VLPs) that are morphologically and antigenically analogous to wild-type Norwalk virus. Mice inoculated subcutaneously with VRPs expressing the Norwalk virus capsid protein (VRP-NV1) developed systemic and mucosal immune responses to Norwalk VLPs, as well as heterotypic antibody responses to the major capsid protein from another genogroup I NLV strain (NCFL) isolated from a recent outbreak. A second Norwalk virus capsid clone (NV2) containing three amino acid codon mutations from the NV1 clone was also expressed using VEE replicons (VRP-NV2), but upon infection of BHK cells failed to confer VLP self-assembly. Mice inoculated with VRP-NV2 elicited reduced systemic and mucosal immune responses to Norwalk VLPs, demonstrating the importance and potential utility of endogenous VLP presentation for maximum immune induction. Inoculation with either VRP-NV1 or VRP-NV2 resulted in serum antibody responses far superior to the induction in mice dosed orally with VLPs that were prepared using the VEE-NV1 replicon construct, a regimen similar to current models for NLV vaccination. Expression of NLV VLPs in mammalian cells offers a powerful approach for the design of novel NLV vaccines, either alone or in combination with current vaccination models.

Early childhood diarrhoea and helminthiases associate with long-term linear growth faltering

BACKGROUND

Although the acute mortality from diarrhoeal diseases is well recognized, the potentially prolonged impact of early childhood diarrhoea on background growth and development is often overlooked. To examine the magnitude and duration of the association of early childhood enteric infections with growth faltering in later childhood, we investigated associations of early childhood diarrhoea (0-2 years) and intestinal helminthiases with nutritional status from age 2 to 7 years.

METHODS

Twice-weekly diarrhoea surveillance and quarterly anthropometrics were followed from 1989 to 1998 in 119 children born into a Northeast Brazilian shantytown.

RESULTS

Diarrhoea burdens at 0-2 years old were significantly associated with growth faltering at ages 2-7 years, even after controlling for nutritional status in infancy, helminthiases at 0-2 years old, family income, and maternal education by Pearson correlation, multivariate linear regression, and repeat measures analysis. The average 9.1 diarrhoeal episodes before age 2 years was associated with a 3.6 cm (95% CI : 0.6-6.6 cm) growth shortfall at age 7 years. Early childhood helminthiasis was also associated with linear growth faltering and a further 4.6 cm shortfall (95% CI : 0.8-7.9 cm) at age 7 years.

CONCLUSIONS

Early childhood diarrhoea and helminthiases independently associate with substantial linear growth shortfalls that continue beyond age 6 years. Targeted interventions for their control may have profound and lasting growth benefits for children in similar settings.

Viral causes of diarrhea

Viruses are important causes of diarrhea. In healthy adults, the main clinical manifestation is acute, self-limited gastroenteritis. Advances in molecular diagnostics have shown that epidemics of acute gastroenteritis most frequently are due to caliciviruses spread through contaminated food or through person-to-person contact. Application of similar technology is needed to make a definitive statement about the role of such candidate viruses as rotavirus, astrovirus, and adenovirus as the cause of nonepidemic acute gastroenteritis in adults. Rarely a previously healthy adult gets acute CMV colitis. CMV and EBV mainly cause diarrhea in immunocompromised patients, however. Advances in prophylaxis and treatment have reduced the frequency and severity of these diseases. Acute infantile gastroenteritis is caused by rotavirus, calcivirus, astrovirus, and adenovirus. These viral diseases of the gut are seen by the physician as routine and rare clinical problems.

Diagnosis of noncultivatable gastroenteritis viruses, the human caliciviruses

Gastroenteritis is one of the most common illnesses of humans, and many different viruses have been causally associated with this disease. Of those enteric viruses that have been established as etiologic agents of gastroenteritis, only the human caliciviruses cannot be cultivated in vitro. The cloning of Norwalk virus and subsequently of other human caliciviruses has led to the development of several new diagnostic assays. Antigen detection enzyme immunoassays (EIAs) using polyclonal hyperimmune animal sera and antibody detection EIAs using recombinant virus-like particles have supplanted the use of human-derived reagents, but the use of these assays has been restricted to research laboratories. Reverse transcription-PCR assays for the detection of human caliciviruses are more widely available, and these assays have been used to identify virus in clinical specimens as well as in food, water, and other environmental samples. The application of these newer assays has significantly increased the recognition of the importance of human caliciviruses as causes of sporadic and outbreak-associated gastroenteritis.

Seroprevalence and seroincidence of Norwalk-like virus infection among Brazilian infants and children

To determine the importance of Norwalk-like viruses (NLVs) as pediatric pathogens in a developing country, the seroprevalence and seroincidence of this group of viruses in a cohort of children less than 4 years of age in an urban shantytown in northeastern Brazil was examined. Serum samples were collected approximately every 6 months from 135 children who were surveyed three times each week for diarrhea and vomiting. NLV IgG was measured by an enzyme immunosorbent assay (EIA) with recombinant Norwalk virus capsid protein. Overall NLV seroprevalence was 71%, and the overall NLV seroconversion rate was 0.7 seroconversions per child-year. The highest age-specific NLV seroconversion rate (0.8 seroconversions per child-year) was observed in the 13-24-month age group. For all study children, the incidence of diarrhea and vomiting was significantly greater (P < 0.01) during time periods spanned by serum pairs that indicated NLV seroconversion compared with time periods without NLV seroconversion. However, NLV seroconversion was not associated with gastrointestinal symptoms during the first year of life.