Water Sanitation Health

Global burden of disease: impacts of poor water, sanitation and hygiene

A series of new publications, led by WHO in collaboration with 14 leading research institutions, estimates the burden of disease caused by unsafe water, sanitation, and hygiene in 145 low- and middle-income countries. The series begins with a review of global monitoring of burden of disease, authored by Clasen et al. Three systematic reviews then follow, providing up-to-date estimates of the prevalence of poor water, sanitation, and hygiene practices.

Bain et al. review the microbial quality of drinking-water, and present estimates that 1.8 billion people globally use a source of drinking-water that is faecally contaminated. Freeman et al. in their review of handwashing practices, estimate that approximately 19% of the world’s population washes hands with soap after contact with excreta. The Wolf et al. and Freeman et al. systematic reviews use meta-regression to estimate the impacts of poor water, sanitation, and hygiene, on diarrheal disease (Figure 1).

These impacts are then combined with global estimates of key exposures including use of improved water and sanitation, drawing on data from the WHO/UNICEF Joint Monitoring Programme for Water Supply and Sanitation (JMP), and with global figures on diarrhoeal mortality by Prüss-Ustün et al. to calculate the disease burden which could be prevented by improving water, sanitation, and hygiene practices.

Figure 1: Diarrheal disease risk reductions associated with transitions in sanitation and drinking-water

* Estimates of risk reductions associated with transitions to higher levels of service are based on limited evidence and should therefore be considered as preliminary. They are not used in estimating deaths attributable to poor water and sanitation, but suggest that additional health gains could be achieved by transitions to higher levels of service For definitions of improved and unimproved water sources and sanitation facilities, see the JMP website.

Inadequate drinking water and sanitation are estimated to cause 502 000 and 280 000 diarrhoea deaths, respectively. The most likely estimate of disease burden from inadequate hand hygiene amounts to 297 000 deaths. In total, 842 000 diarrhoea deaths are estimated to be caused by this cluster of risk factors, which accounts for 1.5% of the total disease burden and 58% of diarrhoeal diseases. In children under five years old, 361 000 deaths could be prevented, representing 5.5% of deaths in that age group.

The publications are available for download from the journal Tropical Medicine & International Health, and WHO is preparing a brochure to summarize the key findings and highlight policy implications.

1. Bain R, Cronk R, Hossain R, Bonjour S, Onda K, Wright J, Yang H, Slaymaker T, Hunter P, Prüss-Ustün A, Bartram J. Global assessment of exposure to faecal contamination through drinking water based on a systematic review.

2. Clasen T, Prüss-Ustün A, Mathers C, Cumming O, Cairncross S, Colford JM. Estimating the impact of unsafe water, sanitation and hygiene on the global burden of disease: evolving and alternative methods.

3. Prüss-Ustün A, Bartram J, Clasen T, Colford JM, Cumming O, Curtis V, Bonjour S, Dangour AD, De France J, Fewtrell L, Freeman MC, Gordon B, Hunter PR, Johnston RB, Mathers C, Mäusezahl D, Medlicott K, Neira M, Stocks M, Wolf J, Cairncross S. Burden of diarrhoeal disease from inadequate water, sanitation and hygiene in low- and middle-income settings: a retrospective analysis of data from 145 countries.

4. Freeman MC, Stocks M, Cumming O, Jeandron A, Higgins J, Wolf J, Prüss-Ustün A, Bonjour S, Hunter PR, L. F, Curtis V. Hygiene and health: systematic review of handwashing practices worldwide and update of health effects.

5. Wolf J, Prüss-Ustün A, Cumming O, Bartram J, Bonjour S, Cairncross S, Clasen T, Colford JM, Curtis V, De France J, Fewtrell L, Freeman MC, Gordon B, Hunter PR, Jeandron A, Johnston RB, Maüsezahl D, Mathers C, Neira M, Higgins J. Assessing the impact of drinking water and sanitation on diarrhoeal disease in low- and middle-income settings: A meta-regression.