What Are Sexually Transmitted Infections?
Sexually transmitted infections (STIs) are caused by bacteria, viruses, and parasites that are spread through sexual contact. These organisms can be found in vaginal fluids and in semen, on the skin of the genitals and areas around them, and in the mouth, throat, and rectum. Most STIs cause no symptoms or cause symptoms that can easily go unnoticed. Others can cause pain and physical and psychological discomfort. If not treated, some STIs can cause pelvic inflammatory disease, chronic pelvic pain, infertility, and cervical cancer in women, and some STIs can cause infertility, and anorectal and prostate cancer in men. Some STIs can also greatly increase the chance of becoming infected with HIV.