"When you have sex with someone, you are having sex with everyone they have had sex with for the last ten years, and everyone they and their partners have had sex with for the last ten years."
C. Everett Koop, M.D., Former U.S. Surgeon General
"Many teenagers, as well as adults, are indirectly exposed to more than one sexual partner each year because their partner has had sex with someone else."
Alan Guttmacher Institute, 1994