Right now, in a remote corner of rural China, a farmer and his family are sharing their water supply with their livestock: chickens, ducks, pigs, sheep. They share the same waste-disposal system, too. Bird viruses meet their human counterparts in the bloodstreams of the swine, where they mix and mutate before spreading back into the human population. And a new flu is born. Dr. Noah Haldane, of the World Health Organization, knows that humanity is overdue for a new killer flu, like the great influenza pandemic of 1919 that killed more than twenty million people in less than four months. So when a mysterious new strain of flu is reported in the Gansu Province of mainland China, WHO immediately sends a team to investigate.