Chlamydia is a bacterium, a microorganism that invades human cells. Like other sexual infections it can enter your body through sexual contact and the exchange of body fluids like semen or vaginal secretions. It is a concern because if undiagnosed and untreated it can cause serious long term problems that it may not be possible to put right.
A news item by Dr. Christian Jessen posted on the 7th of May 2011.