Doctors observe symptoms, diagnose diseases, and treat patients. Global health experts examine statistics, observe trends, identify mechanisms and linkages, and recommend policy changes on a large scale.
One of the reasons many global health students choose this field is a desire for healthcare equity worldwide. There is certainly reason to be concerned. In Japan, for instance, the average life expectancy is 84.6 years; in the Central African Republic, it is only 53.7. Arguably, disparities such as these amplify global instability and just aren't sustainable.
Global health professionals seek reasons for these variations in terms of factors such as healthcare, population genetics, diet and lifestyle, environment, and whatever else can be quantified. They then identify specific, cost-effective actions that will produce positive health outcomes.
Students of global health need to combine compassion with objectivity, be able to relate to people from various backgrounds, have an interest in medicine and the life sciences, and be skilled at drawing sensible conclusions from masses of raw data.