Chlamydia is the most common sexually transmitted disease in the United States. Chlamydia is a bacteria that is easily transmitted during vaginal, anal, or oral sex. (Chlamydia can also be passed from an infected mother to her baby during vaginal childbirth.) An estimated 2.8 million infections occur each year in the U.S. alone.

One reason chlamydia is so common is that it is often a “silent” infection—most men and women carry the bacteria without showing any symptoms. But chlamydia should be taken seriously because it can impair fertility in women and men.

In women, the bacteria initially infect the cervix and the urethra. Women who have symptoms might have an abnormal vaginal discharge or a burning sensation when urinating. If the infection spreads from the cervix to the fallopian tubes women may still have no signs or symptoms; others may have lower abdominal pain, low back pain, nausea, fever, pain during intercourse or bleeding between menstrual periods.

Men with signs or symptoms might have a discharge from their penis or a burning sensation when urinating. Men might also have burning and itching around the opening of the penis.

Any sexually active person can be infected with chlamydia. The greater the number of sexual partners, the greater the risk of infection. Since chlamydia can be transmitted by oral or anal sex, men who have sex with men are also at risk for chlamydial infection.

Chlamydia is easily diagnosed and is easily treated with antibiotics, so everyone who has any reason to suspect they might be infected should go to a doctor and get tested. Of course, if you are in a sexual relationship with somebody, your partner should be tested to, since if they are positive for chlamydia, you are likely to be re-infected even if you are initially clear of the disease.