Chapter 1 is of course the introductory chapter. Cook introduces the hero (Jack), his profession, his major personality traits, the people he works with, the relationships he has with them, and the conflicts.
There are several conflicts in Contagion, and Cooke introduces all the major ones in Chapter 1. He introduces two of Jack's personal internal conflicts (recklessness, AmeriCare), one of his personal external conflicts (battling unjust externalities; symbol: the taxis), one general external conflict (office politics) and the central external conflict of the novel (nosocomial infection).
Chapter 1 starts out with gusto with Jack begging for trouble (personal and racial trouble) by challenging a New York City taxi driver, with feigned courtesy that thinly disguises a challenge, to a fight.
"Excuse me," Jack Stapleton said with false civility to the darkly complected Pakistani cabdriver. "Would you care to step out of your car ...?"
Jack then follows his "slalom" bike route through New York to the Medical Examiners building. This slalom, incidentally, is the dual symbol of the upcoming adventure and of Jack's personal life that we are told more about as the story unfolds.
Once inside and arrived at his fifth floor office, Jack is told the day's autopsy assignments from which he picks the mystery nosocomial infection. We learn, as Jack interacts with the characters he works with, that nosocomial infection is acquired while in hospital. In other words, this is an infection that, in the normal course of events, a patient would not have gotten if not admitted to a hospital. The hospital in this case is Manhattan General (called "the General"), which is owned by AmeriCare.
Before Jack goes off to begin the autopsy on Donald Nodelman, the man who suddenly died of the nosocomial infection at the General, he tells his supervisor and assignment dispenser, Laurie Montgomery, that it would give him personal satisfaction if he could cause AmeriCare some trouble.
"[It] might make this case personally rewarding," Jack said. "Maybe I'll be lucky enough for the diagnosis to be something like Legionnaires' disease. ... [I'd like] giving AmeriCare heartburn."
During the autopsy that follows, Jack learns surprising and important information about the infection that impels the rest of his actions as the story unfolds.