 Human immunodeficiency virus

Human immunodeficiency virus is the name used for two related retroviruses, HIV-1 and HIV-2, whose infection can lead to AIDS. The virus and the disease stage are distinct: AIDS is the most advanced stage of human immunodeficiency virus infection, rather than the name of every infection.^[ref]

Both belong to Lentivirus, within Orthoretrovirinae and Retroviridae. Their replication connects an RNA genome, a DNA intermediate formed by reverse transcription, and an integrated provirus. In primate lentiviruses, entry involves CD4 and a chemokine receptor; identifying a cell receptor and measuring subsequent virus production are distinct experimental questions.^[ref][ref]

A constructed measurement example distinguishes a molecular quantity from a biological outcome. Suppose an assay reports 100 viral RNA copies in an analysed equivalent of one microlitre of plasma. The corresponding viral load is $100\times 1000=100,000$ RNA copies per millilitre, assuming the assay's stated calibration and volume correction. That count is not a direct count of infectious virions, and it does not by itself specify a person's disease stage. The measured material, normalization and biological question must all be stated.