Why does the author of "The Hot Zone"change from 3rd person perspective to 1st person within the book?

The majority of The Hot Zone is written from the third-person omniscient point of view. Of course, the author is not simply composing characters' thoughts and emotions. This book recounts a true story, and Richard Preston interviewed many, many people to learn directly from those involved. Therefore, the reason the author is able to be omniscient is because he has taken great pains to be accurate in his telling of the tale. If he describes someone's internal reaction to an event, he is relating what that person told him. He is also careful to give credence to everyone's viewpoints in the cases where people have differing recollections of a sequence of events.

There are a few places in which the point of view switches to first person. This is a result of the author's reporting on his interviews with the various people engaged in the crisis at Reston, as well as those involved in earlier Ebola outbreaks. He writes of meeting Gene Johnson at Fort Detrick, talking to Dr. David Silverstein in a coffee shop, and viewing photos of the Ebola virus with Nancy Jaax. This serves to remind the reader that the story is not a piece of fiction, and it also allows the author to tell portions of the story in the participants' own words.