AIDS is a new disease that emerged over the last twenty years. It presents a constellation of clinical features that can affect every body system and pose many challenges for the clinician. Management requires knowledge of the natural history and therapy of HIV infection and AIDS, the diagnosis and treatment of opportunistic infections and HIV-related cancers. The clinical picture is further complicated by the use of a large number of drugs, including the anti-retrovirals and anti-microbial agents.

HIV infection is transmitted by contaminated blood. Epidemiologically, there are differences in developed countries and underdeveloped countries. In developed countries, the majority of patients with HIV infections and AIDS are either male homosexuals or intravenous drug users. In Africa and other underdeveloped countries, the majority of cases are due to heterosexual activity.

The different phases of the disease have been shown to parallel the degree of immunodeficiency as measured by the numbers of CD4 lymphocytes in the blood. However, there are no distinct dividing lines. The different phases form part of a clinical spectrum. Recently, plasma HIV RNA is introduced. This measurement provide a more accurate assessment of disease progression and response to therapy.

A number of antiretroviral drugs are in use for the treatment of HIV infection. The optimal use of these drugs, when they should be started and in what dosage and combination, is the subject of on-going research.

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