Water, sanitation and hygiene : quantifying the health impact at national and local levels in countries with incomplete water supply and sanitation coverage

Overview

This guide aims to assist in the development of a quantitative estimate of health impacts attributable to water, sanitation and hygiene (WSH) related risks at country or local level. Most of data available for the methods used cover developing countries, and this guide is therefore mainly relevant to developing countries. Eleven diseases or injuries are reviewed. For diarrhoea, a calculation method based on access levels to safe water and adequate sanitation service levels is used. The disease burden from malnutrition is linked to WSH risks because of repeated diarrhoea and intestinal nematode infections especially affecting children. Several infectious diseases such as intestinal nematode infections, schistosomiasis, trachoma or dengue in certain regions are almost entirely attributable to WSH-related risks. The fraction of the other diseases, including malaria, lymphatic filariasis, onchocerciasis, Japanese encephalitis and drowning that is attributable to WSH should be estimated based on the basis of expert judgement and, where possible, a systematic review of the literature. Methods for pooling of expert judgement and for systematic literature reviews are outlined in this guide.

The fractions of disease attributable to WSH obtained by the methods outlined in this guide should be combined with national disease statistics for those diseases (deaths, prevalence/incidence or DALYs). Where such national disease statistics are unavailable or of poor quality, approximate estimates may also be obtained from WHO.

The quantification of health impacts and development of understanding of the potential benefits of interventions provide an opportunity to highlight the disease burden that could be prevented through actions in water, sanitation and hygiene. This can assist in directing interventions, and more generally motivate policy action to prevent this disease burden that disproportionately affects children in the lower socioeconomic segments of the population.