The human T cell lymphotropic virus (HTLV)-1 was the first human retrovirus
discovered in 1979 . After the discovery of HTLV-II in 1982,
acquired immunodeficiency syndrome (AIDS) associated retroviruses (ARV) in 1983 and
lymphadenopathy-associated virus (LAV) in 1983, the three prototype viruses (LAV, HTLV-III,
and ARV) were recognized as members of the same group of retroviruses, now known as the
human immunodeficiency virus (HIV) and their properties identified them as lentivirinae.
After the discovery in 1983, HIV was definitively linked to patients with acquired
immunodeficiency syndrome (AIDS) and to groups whose members were at high risk for
developing AIDS in 1984 . The virus that causes AIDS was officially named HIV (human
immunodeficiency virus) by the International Committee on the Taxonomy of Viruses instead of HTLV-III/LAV in May 1986.
The origin of HIV has been traced to the simian immunodeficiency viruses (SIV)
naturally infecting African primates . The SIV variants were introduced to humans
through several independent cross-species transmissions, with each successful zoonotic
transmission resulting in different lineages of HIV . HIV is divided into type 1
(HIV-1) and type 2 (HIV-2), both representing cross-species (zoonotic) infections. Both HIV I and
2 can cause acquired immunodeficiency syndrome (AIDS) in humans . The chimpanzee (SIVcpz)
subspecies Pan troglodytes troglodytes, the inhabitants of the African equatorial forest, is
the primary reservoir of HIV-1, and the virus was
introduced into human populations by at least three independent introductions.
Phylogenetic and statistical analyses have dated the last common ancestor of HIV-1 to around 1910
to 1930 . The origin of ancestral HIV-1 infection is traced to
Leopoldville/Kinshasa in the Democratic Republic of Congo (DRC) . A viral sequence
from 1959 (ZR59) is the oldest known HIV-1 infection . HIV type 2 was originated from
numerous cross-species transmissions of Simian Immunodeficiency Virus (SIV) that are natural
infections of sooty mangabey (Cercocebus torquatus atys) of West Africa.
