The characters in BEATING BACK THE DEVIL include:

A slight, shy physician with a scattering of freckles and a strong sense of privacy, Iwamoto has opted to spend her two years in the Epidemic Intelligence Service in downtown Atlanta, on loan to Georgia's health department. In August 2002, four transplant patients in two states fall inexplicably ill. The problem she uncovers will reveal hidden dangers in the U.S. blood supply.

A shy, wiry-haired doctor with a passion for organ music, Shandera is posted to Los Angeles in 1981 under protest: He thinks he will not find anything interesting to do there. Then Michael Gottlieb, a colleague from residency, contacts him with a tale of young men desperately ill with an unexplained problem that has undermined their immune systems. The paper they write about their investigation will become the first warning of a plague that has since taken millions of lives: AIDS.

The only married couple in the EIS class of 2002, these two doctors—who met in medical school—will find their relationship challenged by the rigorous demands of the EIS. Scott, a specialist in malaria, will be sent to rural Africa, to a town with one road and few resources; when he stands on the unlit road at night to get a cell-phone connection, mongoose run over his feet. Sami will be dispatched to Pennsylvania to lead a foodborne illness investigation; what she finds will trigger one of the largest meat recalls in U.S. history—and may threaten the life she and Scott are building.

A pediatrician who spent summers in Haiti as a teenager—dragged there by his father, who brought the entire family along on volunteer stints—Dowell joins a 1994 deployment to Zaire (now the Democratic Republic of Congo) because his Haiti experience left him with fluent French. He is plunged into the chaos of the almost 1 million refugees who have fled the Rwandan civil war only to find illness and deaths in refugee camps across the Zairean border. Nine years later, he is the chief of a CDC project that has been placed in Bangkok to detect new diseases in Asia when a brand-new disease emerges in Vietnam next door: the anomalous and deadly respiratory infection that will become known as SARS.

The genial chief of the Epidemic Intelligence Service—tall, irreverent, with a taste for Hawaiian shirts—came to the CDC as a mid-life correction. He was already a family physician and microbiologist when he sat down next to an EIS member at his 20th high school reunion. In the fall of 2001, he is enduring a routine meeting when someone taps him on the shoulder: Hijacked airplanes have hit the World Trade Center and the Pentagon. In the urgent days that follow, he will shepherd the EIS through the largest deployment in its history.

He joins the EIS with a mission: Contribute to the final days of the fight against smallpox, the first disease ever eradicated by mankind. In 1973, he lands in a cracked, dingy building in Bangladesh, where he becomes one of the few Western doctors of his generation to treat smallpox patients. Smallpox is chased out of humans—but it becomes one of the most-feared pathogens on the list of possible weapons of bioterrorism. Twenty-eight years later, that knowledge is poignantly useful. Koplan has become the CDC's director, and he must guide the disease-detective agency through the anthrax letter attacks, the first fatal bioterrorist attack on American soil.

As an academic microbiologist, Montgomery spent more than a decade behind a lab bench—except when he was wrestling man-sized poisonous reptiles in Indonesia. He joins the EIS to experience the human impact of disease. He gets more than he bargained for. In the spring of 2003, the CDC sends him to a special assignment, one that requires both disease detection and lab skills. His job will be to untangle the outbreak that closed down a Hanoi hospital and alerted the world to the danger of SARS.