By Dr Ananya Mandal, MD
Chlamydia infection is caused by the bacterium Chlamydia trachomatis and is one of the most common sexually transmitted diseases in the world.
Mode of transmission
The infection spreads from infected individuals to their sexual partners via unprotected vaginal, oral or anal sexual intercourse. Sharing unwashed sex toys or those that are not covered with a new condom may also lead to spread of the infection.
Penetrative sexual intercourse is not always necessary for the infection to be contracted; just contact with sexual bodily fluids from an infected person is enough to lead to the infection. If the eyes come into contact with infected fluids, an eye infection called trachoma may develop, which is the world's leading cause of blindness.
Another method by which the infection can be transmitted is vertical transmission from mother to baby as the baby passes through the vaginal canal of an infected mother.
The Chlamydia bacteria invades and infects the host cells, which they depend on to provide them with nutrients for survival. If the human cells infected by the bacteria are starved of these nutrients, the bacteria die off too.
Once the Chlamydia bacteria are starved of nutrients such as vitamins or iron, they stop dividing and grow to an abnormally large size. However, these aberrant cells can remain viable, as they can adopt a normal state that is ready for division again once the host cell conditions normalize.
Studies have shown that around half of infections clear within a year, while 80% disappear in two years and 90% within three years of initial infection. However, some infections persist and may lead to serious problems such as pelvic inflammatory disease in women and epididymis in men. The bacteria can cause infertility in both men and women.
Reviewed by Sally Robertson, BSc
Last Updated: Jan 14, 2014