Water, sanitation and hygiene have important impacts on both health and disease.​
 

Water-related diseases include:​ 

• those due to micro-organisms and chemicals in water people drink;​ 

• diseases like schistosomiasis which have part of their lifecycle in water;​ 

• diseases like malaria with water-related vectors;​ 

Water also contributes to health, for example through hygiene.​

 

Poor water quality continues to pose a major threat to human health. Diarrhoeal disease alone amounts to an estimated 4.1 % of the total DALY global burden of disease and is responsible for the deaths of 1.8 million people every year (WHO, 2004). It was estimated that 88% of that burden is attributable to unsafe water supply, sanitation and hygiene and is mostly concentrated on children in developing countries.​
 

A significant amount of disease could be prevented especially in developing countries through better access to safe water supply, adequate sanitation facilities and better hygiene practices. In order to allow informed decision-making on interventions aimed at disease prevention and control, it is crucial to carry out a sound economic evaluation of the various options available in specific settings.