AIDS Acquired immune deficiency syndrome, or AIDS, is a recently recognized disease. It is caused by infection with the human immunodeficiency virus (HIV). AIDS is a complicated illness that may involve several phases. It is caused by a virus that can be passed from person to person. AIDS impairs the human body's immune system--the system is responsible for warding off disease--and leaves the victim susceptible to various infections. AIDS was first conclusively identified in the United States in 1981, when 189 cases were reported to the Centers for Disease Control. Within a decade the dise