This book is about the CDC's Epidemic Intelligence Service, which goes out and investigates epidemics wherever they occur in the world. It's structured one-epidemic-per-chapter and pretty much every chapter is interesting. There's a chapter on anthrax, on AIDS, West Nile, smallpox, cholera in a refugee camp in Zaire, TB among a transgender community in Baltimore, and of course, SARS.
McKenna is a good writer and this is a page-turner. I hope she writes more books.