Precision global health: beyond prevention and control

“As we step into 2017 and look back at the past year, Zika undoubtedly stands out. 2016 saw the rise and fall of the epidemic in the Americas and worldwide spread of cases, until WHO declared on Nov 18 that the virus and associated consequences no longer constituted a Public Health Emergency of International Concern, but represented a “significant enduring public health challenge requiring intense action”. As such, Zika joined other “enduring public health challenges” to which “intense action” has been directed for a long time, particularly other communicable and vector-borne diseases, on the list of health priorities. With Zika we are almost in uncharted territory: the heterogeneity in the natural history of the disease and transmission pathways still blur the picture of what is likely to be a long-term global health issue. Yet with some other diseases, a wealth of knowledge and seemingly defined course of action have not enabled us to close the chapter.

Much has been achieved on malaria, for example, but progress is fragile and we are still scrambling in areas where the burden persists despite decades of interventions. One major concern is resistance to pyrethroids used in long-lasting insecticidal nets (LLIN), a cornerstone of malaria control. During the 65th American Society for Tropical Medicine and Hygiene (ASTMH) meeting in Atlanta in November, WHO released the results of a study that shows that LLINs provide protection against malaria even in areas with resistance. However, in this issue of The Lancet Global Health, Laura Steinhardt and colleagues report contrasting results of a case control study in Haiti that raises doubts on the usefulness of nets in a low transmission setting, hinting that their mass distribution is not a panacea everywhere. In fact, a session at ASTMH explored key knowledge gaps in malaria interventions and raised thought-provoking questions on what is needed to finally get rid of the disease, given issues of resistance, uncertainties about newer strategies such as seasonal malaria chemoprevention or intermittent preventive treatment for pregnant women, and potential impact of the RTS,S vaccine. As highlighted during the session, there is no silver bullet, and success may only be found by putting multiple axes of pressure on the vector through combinations of interventions. The trick is figuring out what combination works in what setting, and that seems to be the next big question around malaria elimination: how do we develop decision tools to tailor interventions to a set of biological and social determinants—in other words, how do we move on to a more customised approach, through what could be called “precision global health”?

The idea of a “precision” approach to global health is not limited to malaria. Prevention strategies against soil-transmitted helminths (STH) for example have included water, sanitation, and hygiene interventions and mass drug administration, another imperfect and controversial intervention as highlighted in an Article by Vivian Welch and colleagues and two Comments in this issue. In their network meta-analysis, Welch and colleagues found little to no effect of mass deworming on children’s growth, cognition, and school attendance. Eliminating the last pockets of STH incidence and prevalence will therefore require another precision approach, maybe one that combines controlling the parasites with working on more distal determinants of infection such as poverty.

A tailored approach will also help in reaching broader global health targets. The decrease in child mortality during the Millennium Development Goals era has been real but insufficient, and unequal. In some areas progress could be accelerated with more refined targeting of causes of death. Knowing where to target interventions to reduce mortality, by analysing the variability in the distribution of health outcomes for different causes would optimise efforts to reduce child mortality. A study by Marshall Burke and colleagues published in the last issue provides such valuable input, by identifying subnational mortality hotspots across sub-Saharan Africa in which the mortality decline is not on target to reach the Sustainable Development Goals (SDG) by 2030, as well as potential drivers for the difference in mortality. Spatial analyses of this kind provide crucial granular information—in line with a precision approach to global health—that could contribute to the progress towards the SDGs.

So beyond the essential steps of event surveillance and case management, on which the prevention and control of diseases are based, if we are to truly advance health and eliminate diseases, a case can be made for a tailored approach and the advent of precision-style global health.” Lancet – Global Health – Jan 2017


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