Access to safe and reliable drinking water and sanitation, Millennium Development Goal 7, target 7c, is essential for health and well-being (Esrey et al. 1991; Fewtrell et al. 2005; Clasen et al. 2007) and is recognised as a human right (United Nations General Assembly, Resolution 64/292). Hygiene delivers many of the health benefits associated with water and sanitation and yet is missing from the Millennium Development Goals (MDGs). In 2013, the United Nations General Assembly will convene to agree post-2015 goals and targets for sustainable development. Health should not be sidelined in this process (Singh et al. 2012). An updated estimate of the number of lives that could be saved by the practice of good hand hygiene adds weight to the case for this basic life-saving intervention to be included as a measurable indicator of health in the forthcoming goals.
Handwashing with soap (HWWS) is one of the most cost-effective of all public health interventions (Jamieson et al. 2006). Alongside sanitation, HWWS after defecation acts as a primary barrier to faecal–oral spread of diarrhoea by preventing faecal matter from entering the environment, while HWWS before eating reduces transmission from faecal pathogens in the environment (Curtis et al. 2000). Although respiratory pathogens are primarily transmitted via the airborne route, bacteria and viruses shed from the nose, mouth or anus can also be spread via hands and fomites (Goldmann 2000) and campaigns to prevent influenza have tapped into this (United Kingdom Department of Health 2011). The simple action of washing hands with soap can interrupt the transmission of both diarrhoea and pneumonia, the two biggest causes of deaths of children under five (Liu et al. 2012). The latest estimates attribute 0.751 million (uncertainty range 0.538 – 1.031 million) deaths among children aged 1–59 months a year to diarrhoea and 1.071 million (uncertainty range 0.977 – 1.176 million) to pneumonia globally (Liu et al. 2012). In 2003, we estimated the annual number of deaths due to diarrhoea preventable by HWWS at about a million (Curtis & Cairncross 2003). In the light of the revised estimates for child mortality, it is necessary to update these estimates and, in the light of more recent meta-analysis, extend them to include respiratory infections.
There have been a number of reviews of the impact of handwashing with soap on diarrhoea and respiratory infections. For diarrhoea, Curtis and Cairncross concluded that the universal practice of HWWS could reduce the risk of diarrhoea in the community by 47% (pooled estimate, evidence from intervention studies only) or 48% (pooled estimate, reduction in severe outcomes) (Curtis & Cairncross 2003). These estimates were followed by further reviews with a range of different inclusion criteria (Fewtrell et al. 2005; Aiello et al. 2008; Ejemot et al. 2012). Considering all available evidence, the most recent review by Cairncross et al. (2010) took 48% (the reduction in risk of severe outcomes) as the figure for inclusion in the global LiST model (Cairncross et al. 2010). We therefore also used 48% (95% confidence interval [CI] 24–63%) when calculating the number of deaths due to diarrhoea that could be prevented by HWWS.
Reviews have also consistently suggested that HWWS can reduce the risk of respiratory infections. Two reviews concluded that HWWS could reduce the risk of lower respiratory tract infections such as pneumonia by 21% (95% CI 5–34%) (Aiello et al. 2008) and 16% (95% CI 11–21%)(Rabie & Curtis 2006). An update with findings from two subsequent studies (Luby et al. 2005; Sandora et al. 2005) concluded that HWWS could reduce the risk of lower respiratory tract infections such as pneumonia by 23% (Ensink 2004) (95% CI 11–33%). We opted to use the latest, updated estimate in our calculations. We assume that the number of lives saved is proportional to the reduction in disease risk, as in other studies (Curtis & Cairncross 2003; O'Brien et al. 2009; Watt et al. 2009). Table 1 shows that 607 000 deaths from diarrhoea and pneumonia among children aged 1–59 months could be prevented annually by handwashing with soap.
|Preventable cause of death||Type of Estimate||Calculations||Estimated number of lives saved|
|Diarrhoea||Mean||0.751 million × 0.48||360 000|
|Low||0.751 million × 0.24||180 000|
|High||0.751 million × 0.63||473 000|
|Pneumonia||Mean||1.071 million × 0.23||246 000|
|Low||1.071 million × 0.11||118 000|
|High||1.071 million × 0.33||353 000|
|Total||Mean||0.360 million + 0.246 million||607 000|
These estimates for the potential lives that could be saved through scaling up HWWS exclude a number of other important mortality and morbidity outcomes for which there is suggestive evidence of protection. Around 33% of the 3.1 million deaths occurring annually among neonates are due to infectious causes (Liu et al. 2012), and clean birth and post-natal practices – of which handwashing with soap is a component – have been estimated to reduce death due to sepsis and tetanus by as much as 40% (Blencowe et al. 2011). Although birth attendant and maternal handwashing could save additional lives, low-quality evidence dissuades us from hypothesising the extent of this impact here. Hand hygiene could further reduce mortality from hospital-acquired infections and maternal sepsis (Seale et al. 2009; World Health Organisation 2009). In addition to saving lives, a plethora of other health benefits has been attributed to handwashing with soap, including reductions in healthcare-associated infections (World Health Organisation 2009), puerperal sepsis (Luby et al. 2001), skin infections (Luby et al. 2005), eye infections (Montessori et al. 1998), including trachoma (the latter health improvements come from face washing combined with antibiotic usage) (Ejere et al. 2012), and co-infections and disease progression among people living with HIV/AIDS (Isaac et al. 2008; Filteau 2009). Other benefits include more school attendance as a result of fewer episodes of illness (Bowen et al. 2007; Freeman et al. 2011; Talaat et al. 2011) and possible improvements in child growth and development as a result of improved nutritional status (hypothesised to be mediated via reduction in diarrhoea and environmental enteropathy) (Prüss-Üstün et al. 2008; Bowen et al. 2012). These benefits are described more fully elsewhere (Biran et al. 2012).
Global estimates of this nature carry much uncertainty and are limited by the assumptions made, in particular the use of the risk reduction estimates reported in systematic reviews. Studies included in these reviews were conducted in a variety of income settings and even those studies considered to be of reasonable quality have methodological flaws and differed in when and where handwashing was promoted. Furthermore, the extent to which good hand hygiene can reduce the burden of disease is likely to be mediated by factors such as water and sanitation coverage, prevalence of undernutrition, access to health services, predominant transmission routes and pathogen prevalence across settings. The likelihood that a life will be saved as a result of HWWS is greatest in the poorest, most vulnerable and underserved populations such that the average effects suggested in the meta-analyses may, if anything, underestimate the potential impact in these populations. Estimates such as these are useful in assessing the potential contribution of HWWS to child survival strategies and provide a basis for policy dialogue and advocacy.
HWWS with soap has long been identified as a cost-effective intervention to be scaled up as part of child survival strategies (Black et al. 2003), and new and innovative programmes are demonstrating that hand hygiene behaviour can be improved cost-effectively (Curtis et al. 2011). The absence of a globally binding target that situates HWWS within broader health and development strategies has allowed attention to stray from this potentially powerful intervention. As 2015 and the expiry of the current MDGs draws close, expert groups have begun to formulate a potential hygiene goal (Meeting Report of JMP post-2015 Global Monitoring Working Group on Hygiene 2012) by demonstrating both its utility and measurability. In the mid-nineteenth century, Hungarian Ignaz Semmelweis postulated that doctors' hands spread disease. His handwashing intervention immediately reduced mortality from puerperal fever on affected hospital wards, yet he faced much professional resistance and ridicule for his unsubstantiated ideas (Curtis 2004). The sad story of Ignac Semmelweiss teaches us that sometimes the most obvious solutions are most easily overlooked. In 2013, the global health community must reflect on whether it can afford to overlook such an obvious and cost-effective solution as hygiene again.