International Journal of Epidemiology

p.805-815Objective To identify factors associated with diarrhoea occurrence in children inacityinamiddle income country,with high access to water and sanitation. Methods Acase–control study in the city of Salvador,north-eastern Brazil was conducted from November 2002 to August 2004.Thestudy population consisted of children presenting at health facility. A total of 1688 cases of diarrhoea and 1676 controls were selected. Data collecti on was by a questionnaire and structured observation during home visits.The explanatory variables were grouped according to aconceptual model defined previously. Analysis was done using a hierarchical approach,to provide a more dynamic view of the transmission characteristics of childhood diarrhoea.Non- conditional logistic regression was used,and odds ratio and population-attributable fractions were estimated. Results Socio economic factors contributed most to determining diarrhoea occurrence,followed by interpersonal contact,while factors related to food preparation,the environment and water and sanitation made a smaller contribution. Conclusion The finding sindicate that the transmission of diarrhoeais influenced by factors from all hierarchical levels,with interpersonal transmission playing a relatively higher role than previously thought.This is compatible with a predominance of viruses and other agents spread by interpersonal routes including Shigella, Giardia and Cryptosporidium.Diarrhoea control strategies in similar settings(middle-in come countries in which a large proportion of the population has access to water and sanitation)must give greater emphasis to policie sgeared towards reducing person-to- person transmission for the prevention of diarrhoea