Water, sanitation and hygiene interventions to combat childhood diarrhoea in developing countries

About 3ie The International Initiative for Impact Evaluation (3ie) works to improve the lives of people in the developing world by supporting the production and use of evidence on what works, when, why and for how much. 3ie is a new initiative that responds to demands for better evidence, and will enhance development effectiveness by promoting better informed policies. 3ie finances high-quality impact evaluations and campaign to inform better program and policy design in developing countries. 3ie Synthetic Reviews examine the range of available evidence regarding a particular intervention. SUMMARY This report is a synthetic review of impact evaluations examining effectiveness of water, sanitation and hygiene (WSH) interventions in reducing childhood diarrhoea. The review has been conducted to Campbell/Cochrane Collaboration standards of systematic review, as well as employing mixed methods of data analysis to assess not only which interventions are effective, or not, but why and under what circumstances. The review provides an update of previous reviews conducted in this area, notably Fewtrell and Colford (2004). A comprehensive search was conducted of published and unpublished materials. Studies were identified for inclusion which employed rigorous impact evaluation techniques, using experimental (randomised assignment) and quasi-experimental methods, and which evaluated the impact of water, sanitation and/or hygiene interventions on diarrhoea morbidity among children in low-and middle-income countries. 65 rigorous impact evaluations were identified for quantitative synthesis, covering 71 distinct interventions assessed across 130,000 children in 35 developing countries during the past three decades. Each study was coded for a range of variables relating to type of intervention, effect size and precision, internal validity (relating to evaluation quality) and external validity (relating to context and behavioural mechanisms). Interventions were grouped into five categories: water supply improvements, water quality, sanitation, hygiene and multiple interventions involving a combination of water and sanitation and/or hygiene. Data were collected and synthesised on both quantitative and qualitative information presented in the evaluations. The results challenge the notion that water quality treatment in the household (at point-of-use) and sanitation 'software' (hygiene) interventions are necessarily the most efficacious and sustainable interventions for promoting reduction of diarrhoea. While point-of-use water quality interventions appear to be highly effective – and indeed, more effective than water supply or source treatment in reducing diarrhoea – much of the evidence is from trials conducted over small populations and short time periods. More evidence is needed on sustainability, as water quality interventions conducted over longer periods tend …