Acquired immunodeficiency syndrome: epidemiology, virology, and immunology.

Acquired immunodeficiency syndrome indicates opportunistic infection or unusual malignancy associated with a marked deficiency of cell mediated immunity in the absence of any other cause of the immune defect. This review examines epidemiology, virology, and immunology associated with this disorder. The syndrome appears to be caused by infection of at-risk individuals by a retrovirus that has tropism for a specific population of T lymphocytes.