An international traveler reaches into the snack bowl at an airport bar before passing her credit card to a waiter. A business meeting begins with a round of handshakes. A man coughs on a crowded bus... One contact. One instant. And a lethal virus is transmitted. When Beth Emhoff returns to Minneapolis from business in Hong Kong, what she thought was jet lag takes a virulent turn. Two days later, she's dead in the ER and the doctors tell her shocked and grieving husband they have no idea why. Soon, others exhibit the same mysterious symptoms: hacking coughs and fever, followed by seizure, brain hemorrhage...and ultimately, death. In Minneapolis, Chicago, London, Paris, Tokyo and Hong Kong, the numbers quickly multiply: one case becomes four, then sixteen, then hundreds, thousands, as the contagion sweeps across all borders, fueled by the countless human interactions that make up the course of an average day. A global pandemic explodes. At the U.S. Centers for Disease Control and Prevention, researchers mobilize to break the code of a unique biological pathogen as it continues to mutate. Deputy Director Cheever tries to allay the growing panic despite his own personal concerns, and must send a brave young doctor into harm's way. At the same time, amid a rising tide of suspicion over a potential vaccine-and who gets it first-Dr. Leonora Orantes of the World Health Organization works through the network of connections that could lead back to the source of what they're dealing with. As the death toll escalates and people struggle to protect themselves and their loved ones in a society breaking down, one activist blogger claims the public isn't getting the truth about what's really going on, and sets off an epidemic of paranoia and fear as infectious as the virus itself.

A lethal airborne virus that kills within days becomes a fast-moving, worldwide epidemic. As the medical community races to find a cure and control the panic, ordinary people struggle to survive in a society that is coming apart.