To determine the effectiveness of ceramic filters in reducing diarrhea, we conducted a randomized controlled trial in Zimbabwe and South Africa, in which 61 of 115 households received ceramic filters. Incidence of non-bloody and bloody diarrhea was recorded daily over 6 months using pictorial diaries for children 24–36 months of age. Poisson regression was used to compare incidence rates in intervention and control households. Adjusted for source quality, intervention household drinking water showed reduced Escherichia coli counts (relative risk, 0.67; 95% CI, 0.50–0.89). Zero E. coli were obtained for drinking water in 56.9% of intervention households. The incidence rate ratio for bloody diarrhea was 0.20 (95% CI, 0.09–0.43; P < 0.001) and for non-bloody diarrhea was 0.17 (95% CI, 0.08–0.38; P < 0.001), indicating much lower diarrhea incidence among filter users. The results suggest that ceramic filters are effective in reducing diarrheal disease incidence.

Many people living in developing countries are still reliant on water of poor quality. Figures reported in 2004 by the Joint Monitoring Program showed that, of a population of 734.6 million in sub-Saharan Africa, 56% had no access to a water supply.1 In South Africa, 34% of households did not have access to a water supply in 2000.2 For children younger than 5 years of age in South Africa, diarrhea is the third most important cause of death, after HIV/AIDS and low birth weight, representing 11% of all deaths in that age group.3 Worldwide diarrheal disease is one of the leading causes of morbidity and mortality in developing countries, accounting for 21% of all deaths in children younger than 5 years old and a total of 2.5 million deaths per year.