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Objective: To estimate the prevalence of acute diarrheal diseases (ADD) during the two weeks previous to the interview among children <5 years of age and to describe alarm signs and feeding practices of parents and caregivers (PCG) during children's ADD., Materials and Methods: Analysis of data from the National Health and Nutrition Surveys 2012 and 2006 and the National Health Survey 2000., Results: ADD prevalence decreased significantly from 2006 (13.1%) to 2012 (11.0%), particularly in the lower socioeconomic status. "Frequent bowel movements" were the main warning sign identified by PCG (66.0%) in contrast to "crying without tears" (4.3%) and "blood in faeces" (0.5%); only 42% PCG reported administering oral rehydration therapy. Factors associated with ADD were child's age <1 year and mother's age <20 years., Conclusions: It is necessary to reinforce appropriate ADD preventive and treatment practices among PCG of children <5 years of age.

The present study estimates the prevalence of some enteropathogens in infants and preschoolers with acute diarrhea. From 2006 to 2007, 5459 consecutive stool samples were evaluated. Cryptosporidium parvum was the parasite identified with the higher frequency (5.1%), followed by Giardia lamblia (1.2%). Campylobacter jejuni was isolated in 858 cases (15.7%) and was the most frequent enteropathogen overall. The rates of C parvum, Shigella, and Salmonella were higher in the summer. Rotavirus had the expected winter peak and it was the third enteropathogen because of its frequency. Overall frequency of stool-reducing substances was 15.6% and was associated with a rotavirus-positive test.

Enteropathogenic Escherichia coli (EPEC) is a leading cause of diarrhea in infants less than two years of age in developing countries. To induce diarrhea EPEC uses several virulence factors acting on a still unknown and mysterious mechanism. The hallmark of EPEC infection is a histological intestinal alteration known as the attaching and effacing (A/E) lesion. The bacterium attaches intimately to the enterocyte and induces assembly of cytoskeleton intracellular actin on the cellular surface. Rearrangements of the actin cytoskeleton form a pedestal-like structure where bacterium tightly cups the cells, leading to degeneration of brush border microvilli. Although the mechanism of EPEC-induced pedestal formation has been dissected in detail, the overall mechanism of diarrhea is still obscure. It is believed that EPEC-mediated secretory diarrhea is related to a) intestinal microvilli effacement, b) massive loss of intracellular ions into the intestinal milieu and c) secretion of an EPEC enterotoxin. Epidemiological studies conducted in developing countries have shown that EPEC is one of the main bacteria frequently isolated from children with diarrhea, causing high morbidity and mortality rates. The microbiological diagnosis of EPEC-induced disease is performed with analytic methodologies different from those used by the standard microbiology laboratory, the most relevant being: a) serotypification, b) the adherence assay, c) FAS test, and d) the specific detection of virulence-involved genes (bfpA and eae genes) using molecular biology techniques. The purpose of this review is to update the most recent findings regarding the molecular pathogenesis of EPEC, its epidemiology in Mexico as well as other developing countries, and also the developed methodology for the diagnosis of EPEC infection.

Previous clinical vitamin A trials have found no consistent effect on diarrhoeal disease and respiratory tract infection. These inconsistent results may be due to the distinct effects vitamin A supplementation has among children stratified by factors related to socio-economic status, nutritional status and season. We evaluated the effect of supplementation on the overall incidence of diarrhoeal disease and respiratory tract infections and on the incidence among children stratified by these factors. A total of 188 children, aged 6-15 months, from periurban, marginalized communities of Mexico City were assigned to receive vitamin A ( < 12 months of age, 20,000 IU retinol; >or= 12 months, 45,000 IU retinol) or a placebo every 2 months, and were followed for up to 15 months. Project personnel visited households twice a week to determine the onset and duration of diarrhoeal disease and respiratory tract infections. Vitamin A supplementation had no significant effect on risk of overall diarrhoeal disease but reduced mild watery diarrhoea (incidence rate ratio (RR) 0.69; 95 % CI 0.50, 0.93) and cough with fever (RR 0.69; 95 % CI 0.48, 0.98). Vitamin A supplementation decreased diarrhoeal disease during the summer (RR 0.74; 95 % CI 0.57, 0.94), among non-stunted children (RR 0.69; 95 % CI 0.52, 0.93) and among children from households with better socio-economic measures. Heterogeneity in the response to vitamin A supplementation may reflect heterogeneity in the aetiology and epidemiology of diarrhoeal disease and respiratory tract infections and the impact that supplementation has on the immune response.

Background: Persistent diarrhea (PD) of infancy has incurred high morbidity and lethality. However, decrease in its prevalence, morbidity, and lethality appeared to occur progressively throughout the last decade of the twentieth century. Our objective in this study was to compare prevalence, lethality, and morbidity of infants and children with PD managed in a pediatric referral hospital., Methods: We conducted a comparative cross-sectional study. A total of 546 patients with PD managed during three different periods (1988-1991, 1993-1994, and 1997-1999) were described and analyzed. Prevalence x 100 admissions, prevalence rates of nutritional status, sepsis, pneumatosis intestinalis, carbohydrate and protein intolerance, and lethality were calculated. We used Student t and chi2 tests (alpha = 0.05)., Results: Mean age on admission was 13.8 +/- 24.3 months; 296 (54.2%) patients were males. Prevalence of admissions for PD decreased gradually from 31.7 to 13.8%; rates of lethality and mortality remained unchanged. Malnutrition had high prevalence throughout the three periods evaluated. Rate of carbohydrate intolerance diminished but protein intolerance increased; proportion of pneumatosis intestinalis and bowel perforation did not change. Isolation of Salmonella spp. and small bowel bacterial overgrowth decreased significantly from the 1988-1991 series when compared with later series., Conclusions: Although these observations were made at a pediatric referral hospital, they may suggest that prevalence of PD is diminishing. However, its lethality and mortality rates remain unchanged. Malnutrition persists as a relevant associated factor. Decrease of carbohydrate intolerance and increase in protein intolerance rates resemble rates of children with PD of developed countries. These observations may reflect an epidemiologic transition of PD in Mexico.

Objective: To compare the severity of rotavirus diarrhea (RV) and non-rotavirus diarrhea., Material and Methods: Between October 1994 and March 1995, a cross-sectional study was performed in 520 infants with acute diarrhea, at seven primary care level centers in five states of Mexico. Diagnosis of RV was done through immunoenzymatic assay or electrophoresis. Central tendency measures were used for data analysis. Results were presented as means and standard deviations, or median and variation., Results: RV was isolated from 264 children; most of them were males aged 6 months to 1 year. Differences in clinical manifestations were statistically significant between the rotavirus-positive group and the rotavirus-negative group, in the following variables: median number of stools/24 hours; frequency of vomiting; temperature > 38 degrees C; dehydration; and clinical severity scoring., Conclusions: These results showed a poorer prognosis and a higher severity of rotavirus diarrhea, as compared to non-rotavirus diarrhea in infants.

Human astroviruses (HAstVs) were detected in 23 stool samples from 365 diarrhea episodes among 214 children (<18 months old) prospectively monitored for diarrhea in Mexico City. Stool samples were tested by EIA and reverse transcriptase-polymerase chain reaction (RT-PCR) analysis. EIA was less sensitive (74%) and equally specific, compared with RT-PCR analysis using type-common primers for HAstV detection. Of 31 HAstV isolates, EIA typed 18 (69%) of 26 EIA-positive samples, and RT-PCR analysis typed 26 (84%) of 31 RT-PCR-positive samples. Phylogenetic analysis of the 3' end of the capsid region (363 nucleotides) confirmed the type assignment by EIA and RT-PCR analysis and determined the type for 5 previously untyped samples. Six HAstV antigenic types cocirculated in the community: HAstV-2 (42%), HAstV-4 (23%), HAstV-3 (13%), HAstV-1 (10%), HAstV-5 (6%), and HAstV-7 (6%). RT-PCR and sequence analysis provided more detailed epidemiology of HAstV in the community than did antigenic detection methods.

To determine whether naturally acquired serum IgA and IgG antibodies were associated with protection against rotavirus infection and illness, a cohort of 200 Mexican infants was monitored weekly for rotavirus excretion and diarrhea from birth to age 2 years. Serum samples collected during the first week after birth and every 4 months were tested for anti-rotavirus IgA and IgG. Children with an IgA titer >1:800 had a lower risk of rotavirus infection (adjusted relative risk [aRR], 0.21; P<.001) and diarrhea (aRR, 0. 16; P=.01) and were protected completely against moderate-to-severe diarrhea. However, children with an IgG titer >1:6400 were protected against rotavirus infection (aRR, 0.51; P<.001) but not against rotavirus diarrhea. Protective antibody titers were achieved after 2 consecutive symptomatic or asymptomatic rotavirus infections. These findings indicate that serum anti-rotavirus antibody, especially IgA, was a marker of protection against rotavirus infection and moderate-to-severe diarrhea.

This study was designed to test whether breast-feeding protects infants reared in unfavorable environments from growth-stunting by averting acute infections. The body weight and length, feeding mode and morbidity of 170 healthy infants were assessed at 15-d intervals from birth to 6 mo. Birth weight and length were not different between groups, but at 6 mo, breast-fed infants were heavier and tended to be taller (P = 0.1) than infants fed formula. Relative to NCHS values, infants had lower mean birth weights than a sample of American and European BF infants. At 6 mo, the weight of BF infants caught up to the weight of NCHS standards, while infants fed formula fell to around -1 NCHS-Z-score for weight and length. The cumulative 6-mo weight increments were negatively related to the number of episodes of diarrhea, and positively to duration of lactation (P = 0.03, R(2) = 0.17). The 6-mo length gain was negatively related to infections but not to duration of lactation (P = 0.004, R(2) = 0.19). Never-ill infants attained a better weight (P = 0.04) and length (P = 0.02) than infants who suffered one or more episodes of diarrhea. Weight and length gain of infants suffering at least one episode of diarrhea was positively related to breast-feeding and socioeconomic status. Weight increments of 15-d were positively related to breast-feeding and negatively to the introduction of solids. In conclusion, breast-feeding positively affected the growth performance of the recipient infants by averting infections and possibly by improving nutrient intake during infections.

Objective: Determine the impact of dietary risk factors on patterns of infection by heat labile toxin-producing Escherichia coli (LT-ETEC)., Materials and Methods: Ninety-eight infants were followed from birth for one year in Guadalajara, Mexico, beginning in august of 1986. Stool and breast milk samples were collected weekly from infants and their mothers, respectively. Mothers were also interviewed on a weekly basis regarding the health of the infants. Parametric hazard models were fit to durations of different LT-ETEC disease states determined through the analysis of stools. The child's consumption of supplemental foods and liquids as well as specific levels of LT-ETEC-specific breast milk antibodies were included in each model as time-varying covariates., Results: The hazard of LT-ETEC asymptomatic infection increased 400 percent among children who received oats gruel (hazard rate = 4.01; 95% CI 2.77-5.24). The duration of infection was reduced if the child had had a previous LT-ETEC diarrheal episode (2.12; 95% CI 1.74-2.49) but was prolonged if the child consumed herbal teas (0.53; 95% CI 0.27-0.7). Herbal teas and high LT-ETEC-specific breast milk antibody levels each reduced the hazard of symptomatic infection by ninety percent. Symptomatic episodes became asymptomatic more rapidly if a child was given rice water., Conclusions: Specific weaning foods increase the risk of infection. Breastmilk antibodies and liquid infusions reduce diarrheal disease and infection duration.

Aim: To describe the epidemiologic and clinical characteristics of astrovirus-associated diarrhea in a cohort of young children from a periurban community in Mexico City., Methods: From November, 1988, through December, 1991, a total of 214 children were enrolled in a longitudinal study of diarrhea and monitored from birth to 18 months of age. A stool specimen was collected during each episode of diarrhea. Specimens from a total of 510 diarrhea episodes were tested for astrovirus by enzyme immunoassay and examined for other enteric pathogens. The antigenic types of astrovirus were determined by a typing enzyme immunoassay., Results: Astrovirus was detected in 26 (5%) of 510 diarrhea episodes, with an incidence rate of 0.1 episode/child year; the highest rate was in children 13 to 18 months of age. Astrovirus-associated diarrhea was characterized by a median of 4 stools (range, 2 to 10) during the first 24 h, a median duration of 3 days (range, 1 to 21), vomiting (20%), and fever (7%). No cases of dehydration or repeat symptomatic infections were observed. Coinfection with another pathogen was detected in 11 of the 26 episodes (42%). Serotype 2 (35%) was most common, followed by serotypes 4 (15%), 3 (11%), and 1 and 5 (4% each); 31% were nontypable. Astrovirus-associated diarrhea was less severe, as measured by the number of stools (4.3 +/- 1.9), than diarrhea caused by rotavirus (7.1 +/- 2.8) or when coinfections occurred (5.5 +/- 1.6; P = 0.008)., Conclusions: Astrovirus was associated with 5% of the episodes of diarrhea in this cohort of young Mexican children and presented as a mild secretory diarrhea. Five predominant antigenic types were detected with type 2 being the most common.

Symptomatic and asymptomatic astrovirus infection was prospectively determined in a 3-year birth cohort of Mayan infants. Stool samples from 271 infants and 268 older siblings were tested for astrovirus, adenovirus 40/41, rotavirus and Salmonella, Shigella and Campylobacter species. Concurrent diarrhea, vomiting, fever, or anorexia were noted. Astrovirus was detected in 164 infants (61%) and 20 siblings (7%). Rotavirus (4%) and adenovirus 40/41 (13%) were isolated less frequently. Of all diarrheal episodes reported at a visit, 26% (78/305) were associated with astrovirus; 17% (78/452) of astrovirus infections were associated with diarrhea and 9% with other symptoms. Only diarrhea was associated with astrovirus infection (odds ratio, 1.4; 95% confidence interval [CI], 1.07-1.92; P = .01). Of infants with astrovirus, 70% shed at multiple visits over a period of 2-17 weeks (median, 5). The point prevalence of astrovirus infection was significantly higher among infants than siblings (relative risk, 6.18; 95% CI, 3.93-9.72; P < .0001, chi2). Astrovirus was identified throughout the year, peaked in March and May, and decreased in September. In this population, astrovirus was the most common enteric pathogen isolated; symptomatic infection was prevalent among infants.

It remains unclear whether breast-feeding protects infants against acute respiratory infection (ARI). To determine if breast-feeding protects against ARI as it does against diarrhea, 170 healthy newborns were followed for 6 mo. Feeding mode, incidence and duration of ARI and diarrhea were recorded biweekly. Infants were classified as fully or partially breast-fed, or formula-fed. Incidence and prevalence were computed monthly. The effects of duration of breast-feeding and potential confounders were analyzed by multiple and logistic regression analyses. Incidence and prevalence of ARI were significantly lower in fully breast-fed infants than in formula-fed infants from birth up to 4 mo, as was the mean duration of individual episodes (5.1 +/- 3.5 vs. 6.4 +/- 3.6 d, respectively). Incidence of ARI was negatively associated with duration of breast-feeding and positively associated with the presence of siblings (P < 0.05). The prevalence of ARI was associated only with the duration of breast-feeding (P < 0.05). Infants that were never breast-fed and that had one or more siblings were more likely to have an episode of ARI than those fully breast-fed for at least 1 mo. Incidence, prevalence, and duration of individual episodes of diarrhea were also lower in breast-fed infants. Incidence (r = -0.17, P < 0.02) and prevalence (r = -0.19, P < 0.008) were negatively associated with duration of full breast-feeding. Introduction of solid food was not associated with further episodes of diarrhea. The present results demonstrate protection against ARI as a result of breast-feeding similar to that for diarrhea, i.e., lower incidence and percentage of days ill, and episodes of shorter duration.

Gastrointestinal infections represent a health problem. It is estimated that 1647 million cases of diarrhea and 3.2 million deaths due to this cause occur among children less than five years of age per year. Those belonging to this age group have 15 times more risk of dying because of diarrhea. Cases of liquid acute diarrhea with blood represent 80% of cases, diarrhea with blood represent 10%. Most frequent causes of liquid diarrhea are enterotoxigenic Escherichia coli and rotaviruses and most frequent causes of bloody diarrhea are Shigella, E. coli (EHEC and EPEC). Campylobacter jejuni and Entamoeba histolytica. Annually 15,000 cases of typhoid fever are reported that continue being a public health problem. A negative correlation has been observed between the use of oral rehydration and infant mortality due to diarrhea. After prevention and control measures for cholera, a decrease in morbidity and mortality due to diarrhea has been observed. However, to reduce mortality due to this cause, it is necessary to treat the cases of acute dysentery and persistent diarrhea as well as to increase coverage of health care, to standardize the studies of etiology of diarrhea in Mexico, to establish surveillance centers for the study of diarrhea that give information on the distribution, frequency and trends of microbial agents and to achieve standardized microbiological and parasitological studies of etiology of diarrhea that support public health interventions as vaccination and selective administration of antibiotics.

Using an anti-oocyst wall monoclonal antibody-based immunofluorescence assay, the presence of Cryptosporidium parvum was evaluated in children with diarrhea from rural areas (selected from a door-to-door community survey) and from urban areas (patients attending hospitals) in the State of Puebla, Mexico. Prevalences of 9.4% in a rural population (n = 85) and 29.6% in a hospital-based urban population (n = 81). There was no consistent correlation between water source and other environmental data and the presence of C. parvum in stools. It is concluded that C. parvum may be an important pathogen associated with diarrhea in this Mexican state.

During a period of six years (1985-1990), rotavirus G serotypes were investigated in 104 fecal samples isolates according to an immune enzyme assay using specific monoclonal antibodies against serotypes 1, 2, 3, and 4 of the VP7. The serotypes were established in 65 samples (62.5%) and could not be determined in 39 samples. In the 65 classified serotypes, 7 (6.7%) were found to belong to serotype 1, 23 (22.1%) to serotype 2, 12 (11.5%) to serotype 3, and 23 (22.1%) to serotype 4. The occurrence of the four serotypes during the six years was: serotype 3 was present in three of the six years; serotype 2 was detected in two epidemic outbreaks (1989 and 1990); serotype 3 appeared in the second year and was seen in the remainder of the study; and serotype 4 was present in the six years. We conclude that the four serotypes occur in our population and that future efforts to test the efficacy of any vaccine against this virus should evaluate a protective response against the four serotypes.

We studied the relationship between IgA anti-campylobacter flagellin antibodies in breast milk samples and protection of breastfed infants living in a rural Mexican village from campylobacter infection. There were fewer episodes of campylobacter infection (symptomatic and asymptomatic combined) in infants breastfed with milk containing specific anti-flagellin antibodies (1.2/child/year, 95% CI 0.6-1.8) versus non-breastfed children (3.3/child/year, 95% CI 1.8-4.8; P < 0.01). Infants breastfed with milk that was anti-flagellin antibody negative by ELISA also had fewer episodes of infection compared with non-breastfed children, but the difference did not reach statistical significance (1.8/child/year, 95% CI 0.7-3.0 versus 3.3/child/year, 95% CI 1.8-4.8, P > 0.05). Breastfeeding has a protective effect against campylobacter infection and is associated with the presence of specific antibodies directed against campylobacter flagellin.

Ninety-eight women-infant pairs were followed for up to 50 weeks in the northern part of Guadalajara, Mexico, from August 1986 to July 1987 as part of a community-based, prospective study of the relation between infant feeding patterns and enterotoxigenic Escherichia coli producing heat-labile toxin (LT-ETEC) diarrheal disease. Strictly formula-fed children had an incidence of diarrhea over three times that of strictly breast-fed infants and twice that of breast-fed and supplementally fed children. Strictly formula-fed infants colonized by LT-ETEC were symptomatic for diarrhea nearly three times as often as strictly breast-fed infants and twice as often as infants receiving a mixed diet. The fitting of parametric hazard models to durations until LT-ETEC colonization revealed that the hazard for the first colonization was time invariant. The hazard of diarrhea increased by 400-500% during the rainy season or among children 3 months of age or older who received avena, a barley drink. The best-fitting hazard models to durations until symptomatic expression of LT-ETEC infection all increased through time. This hazard was inversely impacted by the overall amount of LT-ETEC-specific, immunoglobulin A antibodies the infant received via the mother's breast milk and by the provision of traditional medicinal teas.

The objective of the study was to determine the efficacy and safety of two rice-based oral rehydration solutions, with and without added electrolyte in children presenting acute diarrheal dehydration with high stool output (> 10 mL/kg/h) during a two-hour rehydration period. Twenty-two patients of one to 18 months old were recruited and randomly distributed into two groups: group A received the rice-based solution without electrolytes, and group B received the rice-based solution with electrolytes. A stool output diminishing was observed in both groups and rehydration was achieved in 4.0 +/- 0.9 hours in 21 patients from group A and in 4.6 +/- 0.9 hours in 13 patients group group B. There was not a statistically significant difference between the groups regarding the laboratory results. The rice-based oral rehydration solution without added electrolytes was useful for rehydration of children presenting high stool output, after administering the WHO/ORS recommended formula during a two-hour period.

Between january 1 and october 31, 1991 148 samples of feces corresponding to the same number of children with acute diarrhea, aged 0-2 years, admitted to Hospital O'Horan of the Secretariat of Health in the city of Merida, Yucatan, Mexico, were studied. Stools from 105 (70.9%) patients were described as watery diarrhea; from these samples at least one enteric pathogen was detected in 49 (46.6%): a single pathogen was isolated in 37 (35.2%), and mixed infections were observed in 12 (11.4%). We isolated enterotoxigenic Escherichia coli in 18 (17.1%) samples; a predominance of strains producing only ST (11.4%) was observed. Rotavirus was detected in 14.3%, Shigella spp in 8.6%, Salmonella spp in 5.7%, Giardia lamblia in 4.8%, Campylobacter jejuni in 3.8%, enteroinvasive E. coli in 2.8%, Entamoeba histolytica in 2.8% and adenovirus in 1.9%. From watery samples, 80 (76.2%) were negative for fecal blood, and these were most frequently associated with enterotoxigenic E. coli (17.5%) and rotavirus (12.5%). E. coli LT+ and rotavirus association was observed in two patients, and E. coli ST+ and adenovirus association was observed in another one.

A survey was carried out between May and October, 1991 in eleven federal entities to know the correct household diarrhea case management (EMECADI). It was observed that among the 15,125 children less than five years old the punctual prevalence was of 6.4% (970 children); the incidence in the previous two weeks was 14.5% (1,605 children) and the annual incidence of diarrhea was 4.5 episodes per child per year. Among the children who presented diarrhea in the 24 hours, the following rates were observed: use of oral hydration solution, 17.1%; use of recommended homemade fluids, 63.2%; oral hydration therapy use, 63.2%; increased fluids, 29.9%; correct oral serum preparation, 60.0%; continued breast-feeding, 75.0%; continued feeding, 59.8%; adequate knowledge about seeking care, 12.5%, and drugs use, 53.2%. The reference and nutritional components should improved.

The diarrhoea diseases are priority health problems in all countries of the Third World. The number of the cases of diarrhoea and other intestinal infections have very high morbi-mortality rate in mexican childhood. There are many factors that affect these pathologies, those related to social, economic and cultural aspects seem to be the most important. Although the intestinal viruses are frequent, the enteritis produced by bacteria are more severe and acute. There area also parasites that yield the chronic type disease. In this paper, the most frequent parasites and enteropathogenic bacteria infecting children below 15 years old, either hospitalized or being outpatients from the Hospital de Zona No. 29 del IMSS in México City, were studied. The data obtained were related to the socioeconomic level. A total of 415 stool samples were collected from newborn to 14 years old children over a period of nine months. The samples were classified according to the ages, schooling and number of persons who slept with the child in the same bedroom. The samples were examined by a centrifugal concentration technique and by cultivation. The group of children up to five years old were found to be the most infected by bacteria, while children from 10 to 14 years old were by parasites. Those children whose parents either have not finished the elementary school or can not read and write were the most parasitized (40%), these children were also found to be most infected, as the number of persons who slept in the same bedroom increased, the number of infections per children either by bacteria or parasites, also increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Between January to October 1991, were studied 148 samples of feces corresponding to the same number of children with acute diarrhea. In 41 (27.7%) samples, were found macroscopic or microscopic blood. At least one associated bacterial pathogen capable to produce bloody diarrhea was isolated from 22 (53.7%) of these samples. Were isolated five (12.2%) Salmonella strains, all of them were S. enteritidis; nine (22.0%) Shigella: seven S. flexneri, one S. boydii, and other one S. sonnei; two (4.9%) enteroinvasive Escherichia coli strains, and six (14.6%) Campylobacter jejuni strains. A single associated invasive bacterial pathogen was isolated in 13 (31.7%) children. Mixed culture were found in nine children: five (12.2%) children had invasive pathogens association, and four (9.8%) children had invasive and no invasive pathogens association.

A cohort of 200 Mexican children from a low income periurban community was monitored from birth to the age of 2 years to determine the serotype-specific incidence, morbidity and seasonal pattern of symptomatic and asymptomatic human rotavirus (HRV) infections. A total of 177 HRV infections occurred in 134 (67%) children; 50% of these infections were asymptomatic. The incidence of all HRV infections was 0.6 episode/child year and was inversely related to age (r = -0.93; P < 0.01). The incidence of HRV-associated diarrhea was 0.3 episode/child year, with the highest frequency and severity occurring in infants between 4 and 6 months of age. HRV infections were more frequent each autumn, with a changing sequential pattern of predominant serotypes. Overall serotype 3 (34%) was the most frequent, followed by serotypes 1 (16%), 2 (15%) and 4 (6%). The 4 serotypes were associated with a similar risk for diarrhea and severity of diarrhea. In 23 (26%) HRV diarrhea-associated infections, an additional enteropathogen was identified; these mixed infections were more frequent in older children (chi square, 4.45; P < 0.05) but were not more severe (chi square, 0.02; P > 0.05). Our data indicate that HRV infections were common early in life, seasonal, frequently asymptomatic and caused by a variety of serotypes, none of which was a risk factor for diarrhea or severity of diarrhea.

The following work informs of the results of isolation, frequency and distribution of enteropathogens in children under five years old, without previous antibiotic treatment, less than seven days with diarrhoea, ambulatory or in Hospital "Dr. Ramón Madariaga" de Posadas, Misiones, República Argentina, from June 1986 to May 1989. From a total of 972 children with diarrhoea, 78% required to be hospitalized. The greatest number of cases were found during spring and summer in children from 1 to 11 months of age. Distribution of the main enteropathogens was: enteropathogenic Escherichia coli (EPEC) (29.4%), parasites (22%), Shigella (16.3%), enterotoxigenic Escherichia coli (ETEC) (14%) and rotavirus (12.9%). Highest incidence of rotavirus was registered in the coldest months and Shigella, ETEC, Salmonella and parasites in the warm months. The group of most affected children were from 1 to 11 months of age, with higher incidence of EPEC, Salmonella and rotavirus, and parasites were found in older children. ETEC and Shigella had no relationship with the age of children. The most frequent association was EPEC with rotavirus. This is the first finding of Salmonella zaiman in humans and of Salmonella hadar in Argentina. Cryptosporidium, etiological agent of serious diarrhoea in the immunocompetent, was isolated in 3.9% of our cases.

Colonization of the intestine with Campylobacter jejuni was followed longitudinally from birth in a cohort of 75 rural children with fecal cultures taken every fortnight and every time they had diarrhea. Only 25% of children initially colonized with C. jejuni during the first year of life, and 12% of children initially colonized during the second had diarrhea. The age at which a child was initially infected with C. jejuni was not a risk factor in relation with presence of disease. A higher illness-to-infection ratio (P less than 0.05) was found during subsequent colonization with C. jejuni when initial infection was associated with diarrhea. Risk of diarrhea during initial or subsequent colonization with C. jejuni was not related with the production of cholera-like enterotoxin, a cytotoxic active on HeLa cells or with adhesive ability to HEp-2 cells by the infecting strains.

Stool specimens obtained longitudinally during the first year of life of a cohort of 75 rural infants were tested for the presence of rotavirus with an enzyme-linked immunosorbent assay. Thirty four infants showed the presence of rotaviruses during the first year of life. Only 41% of these episodes were associated with diarrhea. Extraction of rotavirus RNA was still possible in 12 of 34 stool samples, ten of them obtained during episodes of associated-diarrhea. Electropherotyping of these rotavirus showed that nine had a short electropherotype. One diarrheal and two asymptomatic samples had a long electropherotype. Subgrouping the viruses with monoclonal antibodies showed that five of the nine rotaviruses with short electropherotype belonged to subgroup I, and two of the three with long electropherotype belonged to subgroup II. The rest of rotaviruses could not be subgrouped. This study confirms the prevalence of only few rotavirus strains in any defined geographic region over a specific period of time, in this case, a rotavirus with a short electropherotype.

Rotavirus is the major cause of severe diarrhea in children. A recent study of hospitalizations for diarrhea in the United States suggested that the annual rotavirus epidemic may follow a regional sequence from west to east. As part of a program to establish active surveillance of rotavirus prior to the introduction of vaccines, we obtained 5 years of retrospective data on rotavirus detections from 88 centers throughout North America. Analysis of 34,644 detections indicates that the peak of the annual rotavirus epidemic occurs first in Mexico and the Southwest of the United States in late fall, goes systematically across the continent in the winter, and ends in the Northeast United States and the Maritime Provinces of Canada in the spring. When detections are grouped by region, onset of the epidemic follows the same regional sequence as the peak. To our knowledge, this is the only description of a repetitive geographic sequence for the seasonal epidemic activity of a viral agent. Further studies are indicated to determine whether climate, features of the virus itself, or other factors are responsible for this apparently unique pattern. A system of active surveillance can use this pattern to detect natural alterations in the epidemic behavior of rotavirus and to assess the impact of vaccines.

The incidence of colonization by enteropathogenic, enterotoxigenic, enteroinvasive, and enterohemorrhagic Escherichia coli (detected by DNA hybridization with specific radiolabeled probes), Salmonella sp., Shigella sp., Campylobacter jejuni, and rotavirus was related to the presence of diarrhea in a cohort of 75 rural infants followed longitudinally during the first year of life. The study was carried out between August 1985 and February 1987 in the village of Lugar Sobre la Tierra Blanca, in the state of Morelos, 180 km southwest of Mexico City. Intestinal colonization by specific enteropathogens was followed with fecal cultures taken every fortnight and every time a child had diarrhea. Pathogens isolated from cultures taken in the 48 hours prior to the initiation of the diarrheal episode were considered to be associated with the disease. Diarrhea was detected in 82% of the children with initial isolation of enterohemorrhagic E. coli and in 64% of the children with enteropathogenic E. coli or Shigella sp. The risk of diarrhea associated with the initial isolation of other pathogens was lower, at 41% for rotavirus and approximately 25% for enterotoxigenic E. coli, Salmonella sp., and C. jejuni. Initial colonization by the enteropathogens studied, whether or not they were associated with diarrhea, prevented disease, but not colonization by the same organism, when the children were reinfected during the first year of life. Enteropathogenic E. coli adherence factor, human or porcine heat-stable enterotoxins, fimbrial colonization factor antigens, and Shiga-like toxins I and II were important pathogenic characteristics related to the presence of diarrhea and to protection against subsequent infection by the same organisms.

A community-based, case-control study was conducted during the summer peak season for diarrhea in the highlands of Chiapas, Mexico, to identify risk and protective factors associated with acute diarrhea in children less than 6 years of age. To estimate the diarrheal morbidity rate, the community was divided into 13 sectors, each of about 20 households. A resident (volunteer mother) made daily visits to every household in her sector to identify new cases of diarrhea. During 3 weeks of surveillance, 63 children with diarrhea and 48 control children were identified. The diarrheal attack rate during this period for children less than 6 years of age was 30%. Analysis of 29 neighborhood-matched case-control pairs showed that children with diarrhea were more likely than their controls to have had a mother with diarrhea in the 2 weeks preceding the onset of the child's diarrhea (P less than 0.05; relative risk = 10). The association of childhood diarrhea with maternal diarrhea may serve as a focus for more detailed studies as well as an intervention that may be appropriate and effective for this community.

A case-control study was conducted in the highlands of Chiapas, Mexico, to identify factors associated with acute diarrhea in children less than six years old. The study found that the diarrhea attack rate among the children surveyed during three weeks in the month of August (the peak diarrhea season) was approximately 30%, and that children whose mothers had diarrhea were especially likely to contract the illness themselves. The methods employed could prove relevant to studies in other areas, and the results obtained could provide the basis for more detailed study of the area involved--and for preventive action.

During December 1976 to January-March 1977, 13/53 children less than 5 years of age were admitted with acute enteritis caused by rotaviruses to the Hospital del Niño, DIF. There is already convincing evidence that this new virus will prove to be the most important etiological agent of sporadic acute enteritis in young children.

Of 150 acute diarrhoea paediatric cases admitted to the General Hospital Augustín O'Horán in Mérida, Yucatán, México between January 1986 and December 1986, human rotavirus was detected in the faeces of 48 (32%) either as the sole aetiological agent or in association with other viruses. Adenovirus was detected in faeces of 18 (12%) patients. Rotavirus of the long pattern type (antigenic subgroup II) predominated. Children aged 7 to 12 months were most commonly infected. Rotavirus was detected throughout the year, whereas adenovirus was detected between January and September only. Clinical features of patients with rotavirus and adenovirus infections are compared.

Enteropathogens were investigated as possible agents in pediatric diarrhea occurring in Mexico City during the summer of 1975. Pathogens were identified in 47 (76%) of 62 cases. Rotavirus particles were detected in 16 cases. Enterotoxigenic Escherichia coli was detected in 29 cases; 11 were positive for heat-labile enterotoxin and 18 were positive for only the heat-stable form of enterotoxin. Multiple pathogens were found simultaneously in 15 (24%) of the study population. This study indicates that the etiology of pediatric summertime diarrhea in Mexico City is diverse. ETEC and RV were the most frequently encountered pathogens, yet they frequently occurred together and with other pathogens. ST-only strains of toxigenic E. coli were as frequently recovered as LT-E. coli suggesting that both forms of ETEC must be sought in future field studies.

To address the hypothesis that malnutrition is associated with an increased risk of diarrhea, the authors identified a cohort of 284 Mexican children less than two years of age in order to equally represent different degrees of nutritional status. Nutritional status, defined anthropometrically, was measured at baseline and every three months for a total follow-up period of one year. The occurrence of diarrhea was assessed by weekly home visits. Among the combinations of weight and length examined, weight for age was the strongest predictor of subsequent diarrhea during a three-month interval. Among normally nourished children, the incidence of diarrhea was 3.3 episodes per year; among those mildly malnourished, 3.7 episodes per year (relative risk (RR) = 1.1); and among the moderately malnourished, 6.0 episodes per year (RR = 1.8). Adjustment for demographic, seasonal, and socioeconomic variables only slightly reduced this association. Nutritional status was most strongly related to the occurrence of two or more episodes during a three-month follow-up interval, and this effect was most clearly seen among children with diarrhea in the preceding interval. In a multiple logistic analysis that included potentially confounding variables as well as an autoregressive term to account for the nonindependence of repeated observations, the relative risk of two or more episodes of diarrhea during an interval was 1.8 (95% confidence interval 1.1-2.9) for moderately malnourished children compared with those who were normally nourished or mildly malnourished. These data lend support to the hypothesis that malnutrition predisposes to the occurrence of diarrhea among young children.

Colonization of the intestine by putative pathogens was followed longitudinally in a cohort of 56 infants born during one calendar year in a rural Mexican village with faecal cultures taken every fortnight and every time a child had diarrhoea. The frequency of isolation of pathogens during episodes of diarrhoea was compared with that of matched controls from the same cohort. Incidence of diarrhoea during the first year of life was 98%, diminishing to 93% during the second year. The incidence curves for each year were not significantly different (P greater than 0.1). Isolation of enteropathogenic Escherichia coli, enterotoxigenic Escherichia coli producing heat-stable (ST) and/or heat-labile (LT) enterotoxins and rotaviruses was significantly higher in infants with diarrhoea during the first 2 years of life. In the case of shigella, although no significant differences were found by semester of life, 13 of 16 children in which these strains were found had diarrhoea. Isolation of Salmonella spp., Campylobacter spp. and protozoa were not significantly different in the two groups during the period studied. Strains showing localized adherence to HEp-2 cells or the presence of colonization factor antigens I or E8775 were found with significantly higher frequency in children with diarrhoea. Eighty-two percent of ST+ or LT+ ETEC strains isolated produced one of the three known colonization factors.

Enteropathogenic Escherichia coli (EPEC) often exhibits localized adherence or diffuse adherence to HEp-2 cells. We recently provided evidence that HEp-2 cell-adherent or enteroadherent E. coli (EAEC) not belonging to EPEC serogroups was the cause of diarrhea among U.S. travelers to Mexico. In the present study, we looked for EAEC and EPEC in stool specimens from 154 children with acute diarrhea and 137 well children seen at several outpatient clinics in Guadalajara, Mexico. EAEC showing localized adherence (EAEC-L) was isolated from 13.0% of the patients and 0.7% of the controls (P less than 0.0001). EAEC showing diffuse adherence (EAEC-D) was recovered from 20.8% of the patients and 7.3% of the controls (P less than 0.001). EPEC was isolated from 4.5 and 6.7% of the patients and controls, respectively. Among all enteropathogens, only enterotoxigenic E. coli occurred as commonly (21.4%) as EAEC-D and EAEC-L did in children with diarrhea. Of the EAEC-L strains isolated from children with diarrhea, 20% belonged to recognized EPEC serogroups, and 3.1% of EAEC-D strains belonged to recognized EPEC serogroups. This study suggests that EAEC may be an important pediatric enteropathogen in Mexican children with diarrhea and further supports the observation that adherence to HEp-2 cells may be a marker of virulence independent of EPEC serogroup among E. coli strains.