Chlamydia is a bacterial infection. It causes inflammation of the mucous membranes, usually in the urethra, vagina, rectum and anal area. Chlamydia bacteria can also affect the mouth and throat. Chlamydia infections are among the most common sexually transmitted infections.
Chlamydia infections are usually more severe in people with HIV. A Chlamydia infection raises the risk of transmitting HIV, as the inflamed mucous membranes and their secretions contain a very high level of virus. HIV-negative people with a Chlamydia infection are at a higher risk of becoming infected with HIV because the virus can enter the body more easily through inflamed skin or mucous membranes.