Water, sanitation and hygiene interventions and the prevention of diarrhoea
Biological, behavioural and contextual rationale
Lack of access to safe, clean drinking-water and basic sanitation, as well as poor hygiene cause nearly 90% of all deaths from diarrhoea, mainly in children (1). While 87% of the world's population now have access to improved water sources, 39% still lack access to improved sanitation (2). Moreover, in developing countries 1.1 billion people still defecate in the open, and hand washing with soap is practised, on average, only after 17% of toilet uses (2, 3).
Diarrhoea most often results from the ingestion of pathogens from faeces that have not been disposed of properly, or from the lack of hygiene. A person is classified as having diarrhoea when she or he experiences more than three liquid stools per day (4). During acute diarrhoea, absorption of macronutrients tends to be high, but when diarrhoea continues for 14 days or more, malabsorption can become severe. Repeated episodes of diarrhoea lead to great loss of nutrients and fluids, causing overall weakness and dehydration. Additional electrolyte imbalance can increase mortality risk, while in terms of morbidity, there is growing evidence for long-term burden, such as impaired growth and cognitive function (5).
Primary prevention of diarrhoea through water, sanitation and hygiene interventions is based on reducing the faecal-oral transmission of pathogens, and includes the provision of an improved water supply, water safety planning, household water treatment and safe storage, improved sanitation facilities, and hygiene education. Improved water supplies refer to technologies such as piped household water connections, public taps, standpipes, or protected dug wells, springs or rainwater collection. Improved sanitation facilities may include flush/pour flush toilets to a confined system, improved latrines (e.g. ventilated, with slab), or composting toilets (2). Water safety planning considers the management of water from the source to tap (6). Water treatment may be carried out at source or in the home, and safe water storage takes place in containers, preventing recontamination of water in the household (7). Hygiene education can address a number of practices, including hand washing after toilet use and before the preparation of food (8).
Reductions in diarrhoea incidence have reached 5% for water supply at source, 19% for water quality interventions (results after 12 months), 36% for sanitation interventions, and 47% for hand washing with soap (estimates from pooled analyses) (9, 10). Larger-scale and possibly longer-term interventions may have additional effects, due to a reduction in the circulation of pathogens across households or communities, and a sustained behaviour change. Due to the multiple and frequent infection opportunities in unsanitary environments, the effectiveness of some of these interventions may seem limited, yet they often are a prerequisite to reaching the next level of sustainable disease reduction (11, 12).
Water, sanitation and hygiene interventions also prevent intestinal parasitic infections alongside diarrhoea, and these infections also have synergistic effects with malnutrition (13–15). Various studies have documented how access to safe water, sanitation and adequate hygiene can predict child growth and malnutrition (16–20).
Behavioural factors are important in determining the uptake and sustainable adoption of water, sanitation and hygiene technologies and practices. While water, sanitation and hygiene interventions are potentially highly efficient, their effectiveness in part depends on behaviour change and context. The installation and functioning of water and sanitation facilities need to be accompanied by the transfer of knowledge on how to use them, together with sustainable behaviour change (9). Maintenance and periodic replacement of existing services/facilities, and hygiene promotion are also necessary to achieve improvements (21).
Low-income countries are particularly affected by deficient water systems and services, poor sanitation and hygiene (1, 2). Implementing water, sanitation and hygiene interventions among poor households would show its highest effectiveness during the first 50% coverage; however, wealthier households are also in need of such interventions (22).
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