http://www.niaid.nih.gov/factsheets/hivinf.htm
National Institute of Allergy and Infectious Diseases, National Institutes of Health
AIDS (acquired immunodeficiency syndrome) was first reported in the United States in 1981 and has since become a major worldwide epidemic. AIDS is caused by HIV (human immunodeficiency virus). People diagnosed with AIDS may get life-threatening diseases called opportunistic infections, which are caused by microbes such as viruses or bacteria that usually do not make healthy people sick. This fact sheet provides information about AIDS, including transmission, early symptoms of HIV infection, diagnosis, and treatment.