A detailed understanding of waterborne pathogen transmission pathways can inform the development and implementation of effective interventions to prevent and control diseases. Such analyses, characterized in the chapter’s third contribution by David Bradley of the London School of Hygiene and Tropical Medicine, highlight the importance of the household as a target for clean water interventions and the critical role of water access, as distinct from water quality, in preventing water-related diseases. In 1972, Bradley and coworkers published the first functional classification of water-related diseases according to their routes of transmission (White et al., 1972). This now widely used scheme structures and clarifies information critical to interdisciplinary efforts to address the health effects of water and sanitation (see also Workshop Overview). Bradley revisits and critically reviews his original taxonomy of water-related disease, and suggests several modifications to incorporate recent research findings, such as the involvement of the respiratory tract in certain water-related diseases (e.g., Legionnaire’s disease; respiratory infections controlled by hand washing).

Taking the same approach to the study of sanitation and disease, Bradley and coworkers identified six sanitation-related transmission categories to inform the choice of preventive measures for a given disease (see Table WO-3 in the Workshop Overview). Bradley presents and explains this classification scheme and describes its possible integration with the functional taxonomy of water-related disease. To further advance the understanding of waterborne disease transmission processes provided by functional taxonomies, he also explores the systematization of hygiene behavior and the spatial structure of water and sanitation services. Finally, in order to assess the relevance of these concepts, Bradley applies them to a real-world system in southwest Uganda.

In much of the developing world, “water is often collected from sources of dubious quality, hauled over a distance, and stored in the home before it is consumed,” observe workshop speaker Robert Tauxe, of the Centers for Disease Control and Prevention (CDC), and coworkers, who contributed this chapter’s final essay. Water gathered in this way is vulnerable to contamination between its source and its point of use, and thus requires the most local of interventions in order to ensure its safety: household water treatment and storage interventions (also known as “point-of-use” strategies). Tauxe and colleagues discuss the concept and practice of point-of-use water treatment and review findings of recent implementation trials of this strategy in diverse settings that demonstrate its impact on public health; some of these trials featured the effective integration of point-of-use interventions with hand washing and other public health strategies. The authors also explore the critical connection between water- and foodborne disease through a series of case studies, all of which illustrate the global effects of local water quality.



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