The clades of HIV: their origins and clinical significance.

It is over 20 years since the identification of HIV as the causative agent of AIDS. Despite the innovation and perseverance of biomedical researchers, HIV has cumulatively infected over 60 million individuals and caused the deaths of over 28 million, the majority in the developing world. There is perhaps no greater need in medical science than the development of more effective treatments for HIV and, ultimately, a protective vaccine. The spread of an extraordinary range of variants of HIV has implications for diagnosis and therapy. As the availability of antiretrovirals increases, data on the clinical response to treatment for non-B subtype infections has increasing relevance. Efficient targeting of the extreme genetic diversity of HIV-1, and an understanding of the processes underlying this, represents one of the major challenges in the control of this ongoing pandemic.