Safe drinking water and better sanitation the key to lowering disease burden

This would be the equivalent of more than 6% of all deaths. The WHO report gives country by country estimates of the prevalence of disease in 193 countries and concludes that 80% of the world's cases of diarrhoea can be put down to unsafe water, inadequate sanitation and poor hygiene, which results in over one million deaths a year, mainly in children.

Furthermore, around 50% of malnutrition is associated with repeated diarrhoea and intestinal nematode infections. The agency estimates that each year underweight in children is responsible for about 70 000 deaths, while unsafe water and poor sanitation and hygiene account for the deaths of 860 000 children under the age of five years.

Similarly, the report says that the burden of blinding trachoma can be "almost fully attributable" to unsafe water and inadequate sanitation and hygiene, and it attributes 66% of the number of cases of lymphatic filariasis disease around the world to the same factors.

WHO analysts say that the benefits of investing in safer drinking water and sanitation far outweigh the costs of the interventions and estimate the savings for health agencies in health care at $7bn a year.

But spending will have to be substantial, the report says. It estimates that outlays of $18bn a year will be needed to meet the United Nations millennium development goal to reduce by half, by 2015, the proportion of people who don't have sustainable access to safe drinking water and basic sanitation.

The UN's development programme and Unicef estimate that more than 1.1 billion people around the world still lack access to safe drinking water and that 2.6 billion people lack access to basic sanitation.