The earliest reports of a new disease were seen in the late seventies-early eighties, after observing rare opportunistic diseases such as Kaposi Sarcoma or Pneumocystis carinii pneumonia, usually occurring in immunodeprimed people, in a cluster of intravenous drug users and gay men in the United States. The syndrome was called AIDS, Acquired Immunodeficiency Syndrome. In Africa, AIDS was first seen in 1982 in Uganda, and shortly after in other countries of the continent. In 1983, scientists from independent research groups in the United States (Gallo et al.) and in France (Barre- Sinoussi et al.) discovered the virus that causes AIDS [1,2]. The virus was at first named HTLV-III/LAV (human T-cell lymphotropic virus-type III/lymphadenopathy-associated virus) and later renamed to HIV (human immunodeficiency virus). The HIV virus belongs to the Retroviridae family. The classification is done by phylogenetic analysis and nucleotidic sequencing of the viruses.