Diarrhea remains a major health issue in developing countries, with high morbidity and mortality rates. Determining the incidence of acute diarrhea in children and its associated factors is crucial to the planning of preventive approaches. The objective of this study was to determine the incidence of diarrhea and to assess some relevant associated factors to it in children younger than 40 months living in two slums of Salvador, Brazil. This is the first prospective cohort, community-based study that was performed in two periurban slums of Salvador, Brazil. Eighty-four children younger than 40 months were randomly selected and visited every other day for one year. The chi-square test was used to evaluate the occurrence of diarrhea and its associated factors. During the surveillance period, 232 diarrhea episodes were identified, resulting in an incidence rate of 2.8 episodes/child/year. In average (mean value of 84 children),each child suffered 11.1 days of diarrhea per year, yielding an average duration of 3.9 days per episode. The highest incidence rates were found among children under one year old. Early weaning, male sex, malnutrition, having a mother younger than 25 years or who considered her child malnourished, missed immunizations and previous pneumonia were associated factors for suffering diarrheal episodes. The rates of incidence and duration of diarrhea that we found are in accordance to those reported by others. Additionally, our results reinforce the importance of environmental and health-related associated factors to the onset of diarrhea.

Several methodological issues may have an impact on the incidence rates of childhood acute diarrhea reported by community-based studies. This study was performed to assess the impact of parental recall ability and definition of diarrhea on the estimate of incidence of acute diarrhea. Eighty-four children younger than 40 months were randomly selected and visited every other day for four weeks and the occurrence of diarrhea was registered. On the last day of the study, another visit was performed and the informants were inquired about the occurrence of diarrhea during the previous four weeks. Data gathered during the four weeks were compared to those obtained on the last visit. Additionally, the informants' definition of diarrhea was investigated and compared to the one adopted by this study. During the observation period, 33 children suffered diarrhea, but only 10 (30.3%) informants reported the occurrence of diarrhea. Although 42.4% of those informants reported that their children had been ill over that period, they did not report diarrhea. Further, 60.6% children who had diarrhea suffered at least one episode in the two weeks prior to the visitation. The same definition of diarrhea used in this study was adopted by 52.1% of the informants inquired. Parental recall is an unreliable method to estimate the incidence of diarrhea and studies with a short interval between the visits should be necessary to correctly evaluate this important health problem. Moreover, assessing the informants' own definition of diarrhea is a significant contribution to the interpretation of the results.

Little is known about the epidemiology of severe rotavirus-associated gastroenteritis in Brazil. Given the morbidity associated with this condition and the importance of having detailed knowledge about the impact of rotavirus infection on the epidemiology of acute diarrhea in children, especially those with the most severe diarrheal conditions, we retrospectively reviewed the medical records of all pediatric patients admitted to a tertiary hospital in Salvador, Brazil, due to rotavirus-associated gastroenteritis during one year. It was observed that rotavirus was responsible for 15.6% of the hospitalizations caused by diarrhea and/or vomiting during the period of the study and that 87 of 218 (39.1%) patients seen at the emergency room with rotavirus-associated gastroenteritis needed to be hospitalized, comprising the population of our study. Most patients presented signs of dehydration, and 41% of them had metabolic acidosis. Most patients (79%) were between six months and four years of age and 72% of the cases occurred in June and July. Gastrointestinal symptoms were rarely present at the beginning of the clinical presentation, and they normally did not last for more than one week.