In the past decade, the world has faced threatening outbreaks of Ebola, Zika, and pandemic influenza. Serious and unforeseen outbreaks of disease may occur naturally or result from or be exacerbated by human activity such as bioterrorism, anthropogenic climate change, laboratory or industrial incidents, or drug-resistant pathogens. Preventing, detecting, and responding to global health security threats requires a comprehensive strategy to protect both collective and individual health, which are closely interrelated. Moreover, the inclusion of the word “global” in the concept of global health security signifies that, in our ever more interconnected and interdependent world, what might appear initially to be the most localized events may in fact have profound international connections and implications.