Disorders frequently seen in AIDS patients include gungal, bacterial, and viral infections, lymphomas; and Kaposi's Sarcoma. The majority of known cases involve homosexual and bisexual men and intravenous drug abusers. Heterosexual transmission accounts for only 4 percent of cases. AIDS is caused by the human immunodeficiency virus (HIV). Antibodies to HIV can be identified by the Elisa and the Western Blot tests. The most important mode of transmission of HIV is through contact with contaminated blood and semen. Consequently, the risk of transmission of HIV can be reduced by safe sexual practices and by avoiding intravenous drug abuse and needlesharing. The drug AZT has shown some promise in the treatment of AIDS, but attempts to develop a vaccine have been less successful. While available evidence clearly suggests that AIDS cannot be spread through casual contact with infected individuals, precautions, such as use of protective clothing and adequate sanitation, have been recommended for health care and emergency workers.