What is chlamydia? Chlamydia is the most commonly reported bacterial sexually transmitted disease (STD) in the United States, according to the Centers for Disease Control and Prevention (Source: CDC). Chlamydia is caused by an infection of the genital tract by the bacterium Chlamydia trachomatis. Chlamydia is preventable and treatable. It is diagnosed by testing a small sample of cells or discharge taken from a woman’s cervix or a man’s urethra. Any person who engages in sexual activity can contract and pass on a chlamydia infection. This includes heterosexual, homosexual, and bisexual men and women. The more sexual partners a person has, the greater the risk of catching a chlamydia infection. Girls and young women have an especially high risk of catching chlamydia. Chlamydia can also be passed from an infected mother to her newborn during vaginal delivery. This can create serious medical complications for the newborn. Sexual partners of infected individuals should be tested and treated. Although there are often no symptoms or only mild symptoms of the disease, untreated chlamydia infection can lead to serious complications, such as pelvic inflammatory disease and infertility. Using safer sex practices, seeking regular medical care, and seeking early, regular prenatal care can help reduce the risk of serious complications of chlamydia.