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 a woman’s reproductive organs.

Both women and men are affected, although there are far more reported cases of chlamydia in women than 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 usually do not have any symptoms. When they are present, signs and symptoms may include discharge from the vagina in women (or penis in men), lower abdominal pain and lower back pain.

Chlamydia can be diagnosed through a urine test and by testing a fluid sample collected from the cervix or penis. The condition is easily treated with antibiotics. If left untreated, chlamydia can lead to a serious medical condition in women called pelvic inflammatory disease (PID), which can lead to infertility.

Although abstinence is the best way to prevent infection, the risk of transmission may be limited by practicing safer sex (e.g., using condoms, limiting the number of sexual partners). Those diagnosed with chlamydia should immediately inform their current and past sexual partners for testing. Treatment of partners limits the risk of complications and the spreading of infection to other individuals, including re-infection of the original patient.

Because it is more common in younger women, the Centers for Disease Control and Prevention recommends that women aged 25 years or younger receive a screening test annually for chlamydia whether or not they exhibit symptoms.