Origins
Both HIV-1 and HIV-2 are believed to have originated in non-human primates in West-central Africa, and are believed to have transferred to humans (a process known as zoonosis) in the early 20th century.HIV-1 appears to have originated in southern Cameroon through the evolution of SIVcpz, a simian immunodeficiency virus (SIV) that infects wild chimpanzees (HIV-1 descends from the SIVcpz endemic in the chimpanzee subspecies Pan troglodytes troglodytes). The closest relative of HIV-2 is SIVsmm, a virus of the sooty mangabey (Cercocebus atys atys), an Old World monkey living in littoral West Africa (from southern Senegal to western Côte dIvoire). New World monkeys such as the owl monkey are resistant to HIV-1 infection, possibly because of a genomic fusion of two viral resistance genes.HIV-1 is thought to have jumped the species barrier on at least three separate occasions, giving rise to the three groups of the virus, M, N, and O. There is evidence that humans who participate in bushmeat activities, either as hunters or as bushmeat vendors, commonly acquire SIV. However, SIV is a weak virus, and it is typically suppressed by the human immune system within weeks of infection. It is thought that several transmissions of the virus from individual to individual in quick succession are necessary to allow it enough time to mutate into HIV.
This leads to narrowing of the lumen of the vasa vasorum, causing ischemic injury of the medial aortic arch and then finally loss of elastic support and dilation of the vessel. Dissection of the aortic arch is rare due to medial scarring. As a result of this advanced disease process, normal methods of angiography/angioplasty may be impossible for those with suspected coronary artery disease. Intravenous penicillin
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