Infections that are transmitted through sexual contact are referred to as sexually transmitted infections (STIs). These infections are typically spread from one person to another through sexual contact that involves the vaginal area.  However, they can also be transmitted by oral or anal sexual activity, as well as direct skin-to-skin contact. Infectious sexually transmitted diseases can be brought on by bacteria, viruses, or parasites. Many people are infected with sexually transmitted diseases but are unaware of it since they do not exhibit any symptoms. The symptoms that other individuals experience might range from being relatively unnoticeable to extremely bothersome.