The Human Immunodeficiency Virus (HIV) belongs to the Family Retroviridae, RNA retroviruses that use the enzyme reverse transcriptase to convert viral RNA into DNA. There are two forms of HIV that are associated with human disease. HIV-1 is the most prevalent form worldwide. HIV-2 makes up less than 10% of cases and is found almost exclusively in West Africa.
Both forms of HIV consist of a core of ribonucleic acid (RNA) called the genome, a protein component that surrounds the genome called a capsid, and a lipid bilayer envelope that surrounds them both.
