Sexually transmitted infections (STIs), also known as sexually transmitted diseases (STDs), are communicable diseases that are spread through sexual contact. Common STIs include HIV/AIDS, chlamydia, genital herpes, gonorrhea, and syphilis. STIs are transmitted through the exchange of bodily fluids and are caused by bacteria, viruses, or parasites. Symptoms of STIs include unusual discharge, pain during sex or urination, sores or rashes in the genital area, and itchiness or irritation. Abstinence, or refraining from sexual activity, is the only certain way to prevent the transmission of STIs.