A Thorough Guide to Sexually Transmitted Infections An STI, or sexually transmitted infection, is an infection that has been contracted and spread from sexual contact. Previously, the term STD (Sexually Transmitted Disease) has been used to describe such an infection; however, the term disease should be used to describe a complication of a sexually transmitted infection. A sexually transmitted disease is more severe than the initial infection. Both men and women are vulnerable to STIs, with the…