<p>As someone who has a close relative working in global health, I can tell you that the best way to get into the field is to emphasize the “health” part - get a degree in one of the health professions. The world is full of “idea rats” who like to tell everyone what to do and the health professionals often resent those who haven’t gotten their hands dirty directly dealing with the problems involved. Take a look at the leadership of WHO or any other global health organization - they are almost always health professionals, whether that is physicians, pharmacists, epidemiologists, etc.</p>