Chlamydia is caused by infection with the bacterium Chlamydia trachomatis, which can infect the reproductive tract, urinary tract, or anus. Chlamydia is spread through sexual contact with an infected person including vaginal, oral, and anal sex. Even if a person has no symptoms, they can still spread the infection to others. It is also possible for a pregnant woman to spread chlamydia to her child during delivery, causing an eye infection or pneumonia in the newborn.
