Chlamydia is a common sexually transmitted disease (STD) caused by a bacterium called Chlamydia trachomatis. If left untreated, it can cause numerous medical problems, including serious damage to the reproductive organs.

Both women and men are affected, although there are far more reported cases of chlamydia in women than in men. It is transmitted through vaginal, anal and oral sex, but can also be passed from an infected mother to a newborn during vaginal childbirth. Younger women and those with multiple sexual partners are among those at a higher risk for chlamydia infection.

Most people with chlamydia do not usually have any symptoms. When they are present, signs and symptoms may include discharge from the vagina or penis, genital itching and lower abdominal pain. Because of the similarity in their symptoms, chlamydia is often mistaken for gonorrhea.

Chlamydia can be diagnosed through a urine test and by analyzing a fluid sample collected from the cervix or penis. The condition is easily treated with antibiotics. If left untreated, women with chlamydia may develop a serious infection of the uterus, fallopian tubes and other reproductive organs known as pelvic inflammatory disease (PID). In men, chlamydia can lead to a painful disease called epididymitis, which causes the testicles to swell. Both of these complications can lead to infertility.

Although abstinence is the best way to prevent infection, the risk of transmission may be reduced by practicing safe sex (e.g., using condoms, limiting the number of sexual partners). Those diagnosed with chlamydia should inform their current and past sexual partners immediately so they, too, can be tested for the STD. Treatment of partners reduces the risk of complications and of spreading the infection to other individuals.