We wish to thank the many individuals who contributed to our understanding of the issues presented in this document. Special thanks are due to Dr. Michael Wilson (University of Colorado) and Dr. William C. Reeves (Centers for Disease Control and Prevention, Atlanta, Georgia) for their contributions and review of the early drafts of this manuscript. We thank Dr. Joel Baseman, Dr. Darryl See, Dr. Harold Watson, Dr. Barry Cole, Dr. Joe Tulley, Dr. Chuck Engel, Dr. Shyh-Ching Lo, and Dr. Garth Nicolson for helpful discussions pertaining to the Mycoplasma chapter. We also thank Dr. Donald Henderson (Johns Hopkins School of Public Health) and Dr. Robert Chen (CDC).