The U.S. Centers for Disease Control and Prevention estimates that more than 4 million new cases occur each year The highest rates of chlamydial infection are in 15 to 19 year old adolescents regardless of demographics or location. Chlamydial infection is caused by a bacterium, Chlamydia trachomatis, and can be transmitted during vaginal, oral, or anal sexual contact with an infected partner. A pregnant woman may pass the infection to her newborn during delivery, with subsequent neonatal eye infection or pneumonia.
Most chlamydial infections are silent, causing no symptoms.
However, men and women may experience abnormal genital discharge or pain during urination. These early symptoms may be mild. If symptoms occur, they usually appear within one to three weeks after exposure. Two out of every three infected women and one or two out of every four infected men have no symptoms. Often, these infections are not diagnosed until PID or other complications develop.