Home > Infectious Disease > What are Sexually Transmitted Diseases? Get the Flash Player to see this player. Rate: (Click the stars to rate) Published on Aug 22, 2008 by TKelly, Views: 5638 Sexually Transmitted Infections (STD's) are infections that are obviously transmitted during sex. Ways to prevent STD's are abstinence or not having sex, protection- condoms, and being in a monogamous relationship. Chlamydia, and gonorrhea are the most common STD's. They can cause problems such as infertility.