Chlamydia: A type of bacteria one species of which causes an infection very similar to gonorrhea in the way that it is spread, the symptoms it produces, and the long-term consequences.

Like gonorrhea, chlamydia is found in the cervix and urethra and can also live in the throat or rectum. Like gonorrhea, it is highly destructive to the tubes (the fallopian tubes), the conduits through which the eggs voyage from the ovary to the womb. As a consequence, it causes infertility and tubal pregnancies (pregnancies that implant ectopically in the tubes, a potential disaster). Again like gonorrhea, chlamydia is a prime cause of severe pelvic inflammatory disease (PID). Because women newly infected with chlamydia tend not to have symptoms (to be "silent" or symptom-free), chlamydia often goes undetected and untreated, the disease can progress in a stealthy way to wreck extensive destruction of the fallopian tubes and lead to infertility. Once again like gonorrhea, chlamydia is associated with an increased incidence of preterm births (premies). Women with a history of chlamydia have an increased risk of developing cancer of the cervix.

The infant can also acquire the disease during his or her passage through the birth canal, leading the baby to have eye disease or pneumonia. This is one of the reasons that all newborns are treated with eye drops after birth. The drops contain an antibiotic which treats chlamydia. Treatment of all newborns is routine because of the large number of infected women without symptoms and the dire consequences of chlamydial conjunctivitis to the newborn.

Chlamydia can cause a spectrum of disease in men including urethritis (inflammation of the urethra), epididymitis (inflammation of the epididymis) and proctitis (inflammation of the rectum).

About 4 million Americans -- most of them teenagers and young adults -- contract chlamydia each year. Home tests for chlamydia may help prevent the long-term complications of the infection. The home test for chlamydia has been available since 1996. Before that, the infection was detected only through swab samples taken by doctors. The home test involves mailing a urine sample to a lab, saves time and provides privacy.