Human Immunodeficiency Virus, infectious agent that causes acquired immunodeficiency syndrome (AIDS), a disease that leaves a person vulnerable to life-threatening infections. Scientists have identified two types of this virus. There is no cure or effective vaccine for HIV infection. Efforts at prevention have focused primarily on changes in sexual behaviour such as the practice of abstinence and the use of condoms. Attempts to reduce intravenous drug use and to discourage the sharing of needles have also led to a reduction in infection rates in some areas. Moreover; Stigma remains the single...