History of HIV/AIDS: Difference between revisions - Wikipedia

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=== The unresolved issues about HIV origins and emergence ===

It is clear that the several HIV-1 and HIV-2 strains descend from SIVcpz, SIVgor, and SIVsmm viruses,<ref name=Santiago2005/><ref name=VanHeuv/><ref name=Plantier/><ref name=Sharp2001/><ref name=Gao/><ref name=Marx2001/> and that bushmeat practice provides the most plausible venue for cross-species transfer to humans.<ref name=Sharp2001/><ref name=Gao/><ref name=Kalish2005/> However, some loose ends remain unresolved.

It is not yet explained why only four HIV groups ([[HIV-1]] groups M and O, and [[HIV-2]] groups A and B) spread considerably in human populations, despite [[bushmeat]] practices being very widespread in Central and West Africa,<ref name=Sousa2010/> and the resulting human [[Simian immunodeficiency virus|SIV]] infections being common.<ref name=Kalish2005/>