WATER, SANITATION AND DIARRHEA - THE LIMITS OF UNDERSTANDING

This paper reviews the application of epidemiological understanding of diarrhoeal disease to interventions in water and sanitation. Over the past 20 years, great efforts have been made to elucidate the relation ships between water supply, sanitation and diarrhoeal disease. At the outset, it was hoped that improved understanding of these relations co uld provide a rational framework for the planning of public health eng ineering interventions. This paper also reviews historical and recent perceptions of water, sanitation, and diarrhoeal disease, and summariz es progress to date. On the one hand, some fundamental ideas about the relative importance of water quality and quantity in the transmission of diarrhoeal disease have changed, and there is increased recognitio n of the complex interrelationships between interventions, hygiene beh aviour and health. On the other hand, our understanding of the impact of interventions is painfully incomplete, and is unlikely to improve d ramatically in the near future. While further research can usefully il lustrate a variety of interactions in specific contexts, globally appl icable planning guidelines and design criteria appear a dangerous will -o'-the-wisp. While we know more than ever before about water, sanitat ion and diarrhoea, much remains unknown, and is perhaps unknowable.