Chlamydia is a disease caused by a bacterium (Chlamydia trachomatis) that is transmitted during sex. It is estimated that 3 million new cases of sexually transmitted chlamydia occur each year. Of those reported cases, most are among young women between the ages of 15-24 years. Many women do not experience symptoms and are only diagnosed by routine screening. When symptoms appear in women they can include vaginal discharge (cloudy fluid), pain during urination, pain during sex, abdominal pain or vaginal bleeding. If left untreated, the infection can spread and cause lasting pain and/or infertility.

Chlamydia often does not produce symptoms in men; experts believe that many infected men go untreated and may give the disease back to their sex partner after treatment or spread the disease to other sex partners. Symptoms in men, when they occur, usually are a cloudy discharge from the urethra (the opening in the penis) and a painful or burning sensation during urination.