David Quammen talks about scary new emerging diseases—such as Ebola, SARS, bird flu, AIDS—and where they emerge from: wildlife. Most are caused by viruses. The phenomenon, when such a virus passes from wild animals into people, is called spillover. Two factors account for the increasing risk of spillovers that may lead to pandemics: disruption (of diverse ecosystems) and connectivity (of the global human population). This is our future.