Chlamydia is the most commonly reported bacterial sexually transmitted infection (STI) in North America, affecting both men and women, although women report the disease more often than men.
The infection is named after the bacterium that causes it, Chlamydia trachomatis. Most women and many men who are infected with the bacteria have no symptoms and therefore don't know they have chlamydia.
Chlamydia is easily treated, but it can sometimes lead to serious complications if it isn't caught early enough. It is estimated that up to 40% of untreated women will develop pelvic inflammatory disease (PID), which can be very painful. The risk of preterm delivery, ectopic pregnancy, or infertility also increases with an untreated chlamydia infection.