The "Spanish flu" virus of 1918 killed an estimated 50 million people, more than all the deaths in World War I combined. While global public health efforts have greatly improved mortality rates in more modern outbreaks, experts say the next pandemic is a matter of "when," not "if." In this episode, Ian Bremmer takes a look how diseases spread and become global. His guest, Dr. Anthony Fauci, is a leading epidemiologist and director of the National Institute of Allergy and Infectious Diseases at the NIH.