The team creates a model of the virus causing an epidemic to better understand how it behaves and affects human cells. The novel virus changes continually, so it is difficult for them to create a vaccine.
A worldwide epidemic starts when humans cut down trees in an area inhabited by bats, forcing them to relocate. One bat carrying the virus dropped a piece of banana into a pig pen. One pig consumed the banana piece, and when it was slaughtered, the virus spread to the butcher's hands. The butcher did not wash his hands before he went to shake the hand of a guest, thus spreading the disease to the guest, who then spread it to other people.
Dr. Cheever and Alan debate the severity of the virus and the steps taken to investigate it. Alan suspects that Dr. Cheever's organization is hiding knowledge because of a Facebook posted written by one of the organization's members. Alan then describes to the public an R0 of two. He indicates that the virus will grow at an exponential rate of 2, infecting a billion people within three months.