A reassessment of the cost-effectiveness of water and sanitation interventions in programmes for controlling childhood diarrhoea.

Cost-effectiveness analysis indicates that some water supply and sanitation (WSS) interventions are highly cost-effective for the control of diarrhoea among under-5-year-olds, on a par with oral rehydration therapy. These are relatively inexpensive "software-related" interventions such as hygiene education, social marketing of good hygiene practices, regulation of drinking-water, and monitoring of water quality. Such interventions are needed to ensure that the potentially positive health impacts of WSS infrastructure are fully realized in practice. The perception that WSS programmes are not a cost-effective use of health sector resources has arisen from three factors: an assumption that all WSS interventions involve construction of physical infrastructure, a misperception of the health sector's role in WSS programmes, and a misunderstanding of the scope of cost-effectiveness analysis. WSS infrastructure ("hardware") is generally built and operated by public works agencies and financed by construction grants, operational subsidies, user fees and property taxes. Health sector agencies should provide "software" such as project design, hygiene education, and water quality regulation. Cost-effectiveness analysis should measure the incremental health impacts attributable to health sector investments, using the actual call on health sector resources as the measure of cost. The cost-effectiveness of a set of hardware and software combinations is estimated, using US$ per case averted, US$ per death averted, and US$ per disability-adjusted life year (DALY) saved.