Chlamydia (klah MIH dee ah) is an infection caused by a kind of bacteria that is passed during sexual contact, or during birth from mother to baby. It is the most common sexually transmitted bacterial infection in the United States. About three million American women and men become infected with chlamydia every year. It is especially common among women and men under 25.  Chlamydia can infect the penis, vagina, cervix, anus, urethra, eye, or throat.
Most people who have chlamydia don’t know it since the disease often has no symptoms.
Chlamydia is the most commonly reported STD in the United States.
Sexually active females 25 years old and younger need testing every year.
Chlamydia can impact a woman’s ability to have children if left untreated.