Acquired Immunodeficiency Syndrome (AIDS) 。1981 In U.S.,cluster of Pneumocystis and Kaposi's sarcoma in young homosexual men discovered.The men showed loss of immune function. 。1983 Discovery of virus causing loss of immune function. Acquired Immunodeficiency Syndrome (AIDS) • 1981 In U.S., cluster of Pneumocystis and Kaposi's sarcoma in young homosexual men discovered. The men showed loss of immune function. • 1983 Discovery of virus causing loss of immune function