A Massive Disease Burden Is Associated with Deficient Hygiene, Sanitation, and Water Supply Top

While rarely discussed alongside the big three” attention-seekers of the international public health community—HIV/AIDS, tuberculosis, and malaria—one disease alone kills more young children each year than all three combined. It is diarrhoea [2], and the key to its control is hygiene, sanitation, and water (HSW).

Figure 1 breaks down the preventable HSW-associated disease burden. It is dominated by mortality from infectious diarrhoea, nearly 90% of which is borne by children under five years old and 73% of which occurs in only 15 developing countries [1]. Moreover, mortality from diarrhoea is only part of the disease burden. Even using the most conservative scenarios, the long-term sequelae due to diarrhoea in early childhood contribute more DALYs than do the deaths [3].

Figure 1. Contributions in DALYs of individual diseases to the total burden of ill-health preventable by improvements in HSW.

PEM, protein-energy malnutrition. Source: [1].

doi:10.1371/journal.pmed.1000367.g001

Regrettably, it is no surprise that much ill health is attributable to a lack of HSW. Globally, nearly one in five people (1.1 billion individuals) habitually defecates in the open. Conversely, 61% of the world's population (4.1 billion people) has some form of improved sanitation at home—a basic hygienic latrine or a flush toilet. Between these two extremes, many households rely on dirty, unsafe latrines or shared toilet facilities [4]. Not only can it prevent endemic diarrhoea, adequate sanitation can help to prevent intestinal helminthiases, giardiasis, schistosomiasis, trachoma, and numerous other globally important infections (Table 1).

Table 1. Environmental classification of water- and excreta-related infections.

doi:10.1371/journal.pmed.1000367.t001

The situation for drinking water appears better than that for sanitation. Although around 13% of the world's population (884 million people) lives in households where water is collected from distant, unprotected sources, 54% (3.6 billion) receives piped water at home. However, many piped water systems in developing and middle income countries work for only a few hours per day and/or are unsafe. In larger Asian cities, for example, more than one in five water supplies fails to meet national water quality standards [5]. Reliable safe water at home prevents not only diarrhoea but guinea worm, waterborne arsenicosis, and waterborne outbreaks of diseases such as typhoid, cholera, and cryptosporidiosis.

Much of the impact of water supply on health is mediated through increased use of water in hygiene. For example, hand washing with soap reduces the risk of endemic diarrhoea, and of respiratory and skin infections, while face washing prevents trachoma and other eye infections. A recent systematic review of the literature [6] confirmed that hygiene, particularly hand washing at delivery and postpartum, also helps to reduce neonatal mortality. It might be argued that water supplies also make flush toilets feasible, but this does not necessarily add to their health benefits, as we have seen no credible evidence that the health benefits of sanitation cannot be achieved by dry latrines, if they are properly built and maintained [7]