AIDS is an infectious disorder that suppresses the normal function of the immune system. It is caused by the human immunodeficiency virus (HIV), which destroys the body's ability to fight infections. Specific cells of the immune system that are responsible for the proper response to infections (T cells) are destroyed by this virus.
Characteristically a person infected with HIV initially experiences no symptoms for a variable period of time. This may be followed by the development of persistent generalized swelling of the lymph nodes (AIDS-related lymphadenopathy). Eventually most patients infected with HIV experience a syndrome of symptoms that includes excessive fatigue, weight loss, and/or skin rashes.