Infection: Preventing 5 Million Child Deaths From Diarrhea

Abstract and Introduction

Abstract

Despite major advances in understanding its prevention and treatment, diarrhea remains a leading cause of global child deaths and a potentially important cause of lifelong morbidity. A new study asks the question: how many lives would be saved by universal scaling up of best practices for diarrhea prevention and control?

Introduction

To quote Rudolph Virchow, "Medicine, as a social science, as the science of human beings, has the obligation to raise such questions and to attempt their theoretical solutions: the politician, the practical anthropologist, must find the means for their actual solution."^[1] In this vein, in 2000, world leaders committed to Millennium Development Goal 4 (MDG4): reduce by two-thirds, between 1990 and 2015, the mortality rate of children under 5 years old. Although recent declines in global child mortality have been encouraging, the rate of decline is insufficient to reach MDG4 by 2015.^[2] MDG4 can still be achieved, but to do so will require substantial reductions in the unacceptably high number of children who die each year from diarrhea (1.3 million child deaths in 2008).^[3]

To that end, Fischer-Walker and colleagues have calculated a first-ever estimate of the effect of a comprehensive scale up of proven interventions for diarrhea mortality in 68 high-priority countries (Figure 1).^[4] Using a Lives Saved Tool (LiST) analysis, their findings suggest that universal access and uptake of breastfeeding, oral rehydration therapy, supplementation with zinc and vitamin A, rotavirus vaccination, provision of antibiotics for dysentery, and basic water, sanitation, and hygiene (WASH) would avert nearly 5 million diarrheal deaths among children over a 5-year period. The total cost of such a strategy would be US$84.^[8] billion, or $3.24 per capita. Of the per capita costs, $0.80 are for non-WASH interventions and $2.44 are for WASH interventions.

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Figure 1.

Percentage of child deaths under 5 years of age averted in 2015 via the universal scale-up of a program for the prevention and treatment of diarrhea in 68 high priority countries. Adapted from Walker, C. L. F. et al. PLoS Med. doi:10.1371/journal.pmed.1000428

Fischer-Walker and colleagues' 'universal scenario' requires that nearly every child be covered by almost all the preventive and therapeutic interventions in order to reduce diarrhea mortality by 92%. A second 'ambitious scenario' presented by these authors represents a more feasible level of intervention (for example, only 50% of children receiving rotavirus vaccination and zinc therapy versus 90% receiving such intervention under the universal scenario) and would result in a 78% reduction in diarrhea mortality. Can either scenario be achieved? The short answer is yes. All the interventions are currently available. All have been proven to reduce diarrhea mortality. Many WASH interventions for diarrhea also reduce childhood growth stunting and thus provide indirect protection against several causes of child mortality. As important as the exciting advances in vaccines are, oral vaccines against rotavirus seem to be substantially less effective in settings where they are most needed (possibly due to either impaired immune responses in malnourished children or to levels of contamination that overwhelm the best of vaccines).^[5] Hence, the scaling up of multiple interventions is likely to have a synergistic effect. Furthermore, the success of any one intervention may depend upon other key interventions.

As acknowledged by Fischer-Walker and colleagues, the major challenges will be the provision of such interventions to the poorest and most vulnerable children in the hardest to reach places. Financing, formulation of national health policies and health campaigns, training of health workers, delivery of services, and strengthening of community-based primary care will require careful coordination by multiple levels of local and national leadership within each country. Scientific discovery and innovation must also continue to have a role by further opening or 'leapfrogging' past current bottlenecks. New approaches to vaccines, diagnostics, therapeutics, water treatment, and the engagement of communities and stakeholders promise to enhance current interventions, extend their effectiveness, and ensure their applicability to local settings.

The exclusive focus of MDG4 on child mortality may miss other equally important benefits of scaling up interventions for diarrhea—such as improvements in children's long-term growth and neurodevelopment. Diarrhea and enteric infections directly contribute to childhood growth stunting and both signal adverse outcomes for children's cognitive development. Diarrheal episodes, cryptosporidiosis, enteroaggregative Escherichia coli infections, and helminthiasis predispose children to growth stunting in the first 2 years of life. By the age of 7, the combined effects of early childhood diarrhea and helminthiasis account for an average height shortfall of 8.2 cm.^[6] Furthermore, early childhood diarrhea or active helminthiasis is shown to predispose children to 4–8% decrements in Harvard Step Test (HST) fitness scores.^[7] Treatment of helminth-infected children or adults with albendazole improves HST scores by 4–7% and adult work productivity by 16%, respectively. Children with heavy burdens of early childhood diarrhea, giardiasis, and/or growth stunting perform poorly on tests of cognitive function in later childhood, with a nearly 10-point decrease in IQ.^[8]

Research by Eppig et al. suggests that the global distribution of cognitive ability (that is, mean national IQ) is determined in large part by global variations in infectious disease, even after controlling for factors such as gross domestic product, education, and malnutrition.^[9] In Northeast Brazil, Guerrant et al. have reported similar findings at the community level in long-term cohort studies of individuals followed from birth.^[6–8,10] By including data on the long-term effects of diarrhea on growth stunting and impaired cognitive function in calculations for disability-adjusted life years (DALYs), the numbers of DALYs due to diarrhea are reported to be increased by 2–6-fold over current WHO estimates.^[11] The value of measures that prevent enteric infections, malnutrition and lasting cognitive impairment is therefore far greater than just preventing the staggering mortality from such infections. Vulnerable children in impoverished areas who don't die of diarrhea and malnutrition are profoundly and chronically affected in ways that we have only just begun to appreciate. In light of these unacceptable costs to human lives, the results from Fischer-Walker et al.'s analyses provide a clear call and game plan to the global community to deliver on key strategies and target reductions in deaths from childhood diarrhea to achieve MDG4. Will we be smart enough and quick enough to respond?

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