Global health arguably represents the most pressing issues facing humanity. Trends in international migration and transnational commerce render state boundaries increasingly porous. Human activity in one part of the world can lead to health impacts elsewhere. Animals, viruses and bacteria as well as pandemics and environmental disasters do not recognize or respect political borders. It is now widely accepted that a global perspective on the understanding of threats to health and how to respond to them is required, but there are many practical problems in establishing such an approach.