Campylobacter infection in developing countries has not received much public health attention because of the observation that infections are not associated with disease beyond the first 6 months of life. A cohort of 397 Egyptian children aged less than 3 years, who were observed twice weekly during 1995--1998, experienced an incidence of 0.6 episodes of Campylobacter diarrhea per child-year. A total of 13% of the Campylobacter diarrheal episodes were characterized by severe dehydration. Age-specific incidence rates (episodes per year) were 0.9 in infants aged less than 6 months, 1.5 in those 6--12 months, and 0.4 and 0.2 in the second and third years of life, respectively. Convalescent excretion of Campylobacter after a diarrheal episode might be enhancing transmission and contributing to this high incidence. Observed risk factors for Campylobacter diarrhea were poor hygienic conditions and the presence of animals in the house. Regardless of the child's age, a first infection by Campylobacter was associated with diarrhea (odds ratio = 2.45; 95% confidence interval: 1.61, 3.71); however, subsequent infections were associated with diarrhea only in children aged less than 6 months. This observation that natural infection did not confer protection during the first 6 months of life poses a challenge to vaccine development.

Reliable epidemiologic data are essential for formulating effective policy to control rotavirus disease through immunization. The objective of this study was to describe the epidemiology of rotavirus diarrhea in a population-based cohort of children under 3 years of age residing in Abu Homos, Egypt, in 1995-1996. Rotavirus diarrhea incidence rates (episodes per person-year) were 0.13 for infants aged <6 months, 0.61 for those aged 6-11 months, 0.17 for those aged 12-23 months, and 0.15 for those aged 24-35 months. Fifty-six percent of children with rotavirus diarrhea had clinical dehydration; 90% of rotavirus diarrheal episodes occurred between July and November. In infants under 1 year of age, receipt of breast milk was associated with a lower incidence of rotavirus diarrhea. No other sociodemographic or environmental factor was found to be significantly associated with rotavirus diarrhea. Of 46 rotavirus isolates with strains identified, 41 (89%) were G serotypes 1 and 2. Rotavirus diarrhea was a major cause of morbidity in this cohort. Promotion of breastfeeding may exert a protective effect in young infants in this setting, but improvements in water and sanitation are unlikely to be effective preventive measures. The use of effective immunization against rotavirus in early infancy should be considered a public health priority.

The incidence of enterotoxigenic Escherichia coli diarrhea among Egyptian children was 1.5 episodes per child per year and accounted for 66% of all first episodes of diarrhea after birth. The incidence increased from 1.7 episodes per child per year in the first 6 months of life to 2.3 in the second 6 months and declined thereafter.Enterotoxigenic Escherichia coli (ETEC) has been recognized as the most common cause of infectious diarrhea in infants and young children in developing countries (14). Manifestations of ETEC infection run the spectrum from asymptomatic infection to severe dehydrating diarrheal illness. The virulence of ETEC is attributed to its ability to colonize the intestinal epithelium via fimbrial adhesive factors and express secretogenic enterotoxins of a heat-labile (LT) and/or a heatstable (ST) variety (10).The epidemiology of ETEC diarrhea was studied in a cohort of Egyptian children in two villages located in the Nile Delta. Children under the age of 24 months at the start of the study and all subsequent new-birth infants were monitored until the age of 36 months or the end of the study was reached. Surveillance for diarrhea was conducted by twice-weekly home visits in which fecal specimens were collected when loose stools were reported (9). For infants, a detailed dietary history (with reference to breastfeeding and the introduction of supplementary liquids and solids) was obtained at each visit. Standard methods were used to detect Salmonella, Shigella, Campylobacter, Vibrionaceae, rotavirus, and astrovirus (8,9,12). Rectal swabs were plated on McConkey's medium, and GM1-ganglioside enzyme-linked immunosorbent assays (11, 13) were used to evaluate five lactose-positive colonies for both LT and ST expression.Diarrheal episodes were defined as beginning on the first day of loose stools after at least three consecutive nondiarrheal days and were considered to have ended when followed by 3 days without diarrhea (9). An episode was classified as an ETEC episode when ETEC was detected at any time during the episode. Children were considered breastfed if they had received any breast milk. To analyze the "time to first episode" of all-cause diarrhea or ETEC diarrhea, Kaplan Meier (KM) curves were constructed for new-birth infants to obtain the distribution of the times to first episode (5). Since exclusively breastfed children usually have loose stools that may be misclassified as diarrhea and no pathogens were isolated in 73% of the diarrheal episodes in the first 3 months of life, the analysis of the time to first episode was restricted to episodes associated with pathogens (ETEC, Campylobacter, Shigella, Salmonella, rotavirus, or astrovirus). Poisson regression models using generalized estimating equations were fitted to adjust for confounding variables (6).In a cohort of 397 children with 211 new-birth infants, 3,477 episodes of diarrhea were detected over 3 years, resulting in an incidence of 5.5 episodes of diarrhea per child per year. Attack rates were highest during infancy (8.1 episodes p...

This study describes the epidemiology of astrovirus diarrhea among a population-based cohort of 397 children aged <3 years residing in rural Egypt from 1995 to 1998. The age-specific incidence rates of astrovirus diarrheal episodes per person-year were 0.38 for infants aged <6 months, 0.40 for those aged 6-11 months, 0.16 for those aged 12-23 months, and 0.05 for those aged 24-35 months. The overall incidence rate of astrovirus diarrhea was the same as that of rotavirus diarrhea, 0.19 episodes per person-year. Astrovirus infection was pathogenic and associated with severe dehydration in 17% of the cases. The most frequent serotype was HAstV-1, and, in order of decreasing frequency, HAstV-5, HAstV-8 and HAstV-3, HAstV-6, HAstV-4, and HAstV-2. In determining whether astrovirus diarrhea was associated with a reduced incidence of subsequent disease, there was evidence to suggest HAstV-1 homotypic immunity but not heterotypic immunity. Because we observed 38% of the incidence of astrovirus diarrhea to occur in infants aged <6 months, a candidate astrovirus vaccine would have to confer immunity very early in life.

To identify enteropathogens for vaccine development, we implemented clinic-based surveillance for severe pediatric diarrhea in Egypt's Nile River Delta. Over 2 years, a physician clinically evaluated and obtained stool samples for microbiology from patients with diarrhea and less than 6 years of age. In the first (N = 714) and second clinic (N = 561), respectively, 36% (N = 254) and 46% (N = 260) of children were infected with rotavirus, enterotoxigenic Escherichia coli (ETEC), Campylobacter, or Shigella. When excluding mixed rotavirus-bacterial infections, for the first and second clinic, 23% and 10% had rotavirus-associated diarrhea, and 14% and 17% had ETEC-associated diarrhea, respectively. Campylobacter-associated diarrhea was 1% and 3%, and Shigella-associated diarrhea was 2% and 1%, respectively, for the two clinics. Rotavirus-associated diarrhea peaked in late summer to early winter, while bacterial agents were prevalent during summer. Rotavirus-associated cases presented with dehydration, vomiting, and were often hospitalized. Children with Shigella- or Campylobacter-associated diarrhea reported as watery diarrhea and rarely dysentery. ETEC did not have any clinically distinct characteristics. For vaccine development and/or deployment, our study suggests that rotavirus is of principle concern, followed by ETEC, Shigella, and Campylobacter.