A genus of gram-negative bacteria which is a parasite living within the cells of humans and other animals, causing a wide variety of diseases. In humans, they cause inclusion conjunctivitis and the venereal (sexually-transmitted) disease by the same name. This STD causes symptoms such as abnormal genital discharge and pelvic pain (in women), but often it produces no symptoms at all. If left untreated, it can cause pelvic inflammatory disease in women (which can lead to sterility and other problems) and, if transmitted during birth, can cause eye infections and pneumonia in newborns. It can be cured with antibiotics.