Abscesses in AIDS. These open sores are infected and contain pus. AIDS (acquired immune deficiency syndrome) is a contagious disease caused by the human immunodeficiency virus (HIV). It causes a gradual impairment of the immune system, which causes otherwise harmless infections to become serious and life-threatening. In cases of severe infection such as this, even antibiotic treatment is slow to have any effect. This patient is from Africa. In the third world, lack of access to drugs and information makes AIDS a major public health problem.