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The word “global” describing something that is worldwide is not a concept that is difficult to understand, whereas the term “health” is frequently misused on the assumption that it simply means freedom from disease. However, health and disease are not merely examples of the converse, a point that is captured by the mission statement of the World Health Organization (WHO), whose objective is to promote health. The WHO definition of health, which is widely used as the definitive descriptor of health, says that health is a state of complete physical, mental, and social well-being and not merely the absence of disease or infirmity. Therefore, global health implies a worldwide mission to promote complete well-being.
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The rational basis for this idea is simple as no nation or region is a complete island in terms of health; what affects one country may well, in time, affect another. The most obvious examples of this concept from past history involve the spread of infections. At present, there is a concerted effort to follow the international spread of HIV or avian influenza. Both present global risks to health, which is the reason why their current distributions are tracked regularly and with accuracy.1 Spread of these diseases has occurred and will continue to occur through a combination of both social and economic factors and the movement of populations and individuals. Yet historically, infectious diseases that have spread rapidly to cause maximum chaos have often resulted from a relatively minor, and often unrecognized, episode rather than a large movement of individuals. For instance, the impact that a localized outbreak of bubonic plague had on medieval Europe when the besieged Genoese garrison in Caffa, in the Crimea, fled by ship bringing the rat host with them was not foreseen.2 The subsequent epidemic, caused by Yersinia pestis, known as the Black Death, reduced the population of Europe by a third over the following 2 years. In addition to the mortality and distress, it resulted in profound social and economic changes that long outlived the epidemic itself. Predicting and tracking the international course of infections is now a key element of global surveillance.
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However, global health problems and disease are not limited to infections, although the propensity to spread is more demonstrable in this group; chronic noninfectious conditions are also global. The relentless increase in the prevalence of diabetes mellitus type 2 in aging populations is such an example. Global health is affected by other factors that include the impact of social, economic, and environmental change on populations. This reflects the fact that human populations are no more isolated socially than they are geographically, but manifest a measure of interdependence where what happens in Kazakhstan may be reflected, in time, in New York City. In the case of diabetes, the causes of changes in health status are different; the international dissemination and adoption of Western dietary behaviors are, at least partly, responsible for this. Health-determining trends such as ...