Sexually Transmitted Diseases (STD) are infections caused by a bacteria or a virus. People usually get STD’s during sex or foreplay when they have contact with infected male semen, vaginal fluids, or skin that often looks normal. Sexually Transmitted Diseases can be serious and painful. If you do not get treatment, some STDs can infect your reproductive organs and you could lose your ability to have kids (Gonorrhea and Chlamydia). Others (HIV, Hepatitis B, and Syphilis) cause general body infections.