Chlamydia is a sexually transmitted disease caused by a bacteria (Chlamydia trachomitis). It is the commonest cause of inflammation of the urethra (the passage urine passes through out of the bladder) that is not caused by Gonorrhoea (non-gonococcal urethritis).
In women chlamydia can infect all the pelvic organs, causing pus to collect in them and chronic pain. Damage to the fallopian tubes which connect the ovaries to the womb (uterus) can result in eggs starting to develop in the tubes instead of in the womb. This is called an ectopic pregnancy and it can kill the mother (deaths from that are counted under maternal conditions, U042). A normal pregnancy can end with the eyes of a baby, born to a mother with chlamydia, becoming infected. Untreated this can cause scarring of the eye, resulting in blindness or low vision. However chlamydia infection often makes it difficult to get pregnant and it is a common cause of infertility.
In men chlamydia can cause inflammation of the urethra (the tube inside the penis through which urine passes), but frequently they don't realize they are infected and infectious. They too can become infertile from chlamydia when the ducts that carry sperm from the testicles (testes) have been damaged by infection.
Chlamydia caused 0.02% of all deaths worldwide in 2002 or 2 deaths per million people, not including deaths due to ectopic pregnancy.