 Influenza pandemics have emerged throughout history, causing widespread illness, death, and disruption, with four occurring in the past century. Globalization and advances in medicine and epidemiology have altered the way these pandemics are experienced, while human development has contributed to their occurrence. While progress in infectious disease prevention, control, and treatment has improved our ability to respond to outbreaks, globalization processes have increased the threat of pandemic emergence and accelerated global disease transmission. Preparedness planning must continue to evolve to keep pace with this heightened risk, and flexible policies are needed to respond to future pandemics with uncertain timing and severity. This article was authored by Patrick R. Saunders-Hastings, and Daniel Kravsky.