Postgraduate medical journal
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All animal life on earth is thought to have a common origin and have common genetic mechanisms. Evolution has enabled differentiation of species. Pathogens likewise have evolved within various species and mostly come to a settled dynamic equilibrium such that co-existence results (pathogens ideally should not kill their hosts). ⋯ These two papers outline the underlying principle of HIV and the differing epidemiologies in Africa, the USA and in Edinburgh. The underlying immunosuppression of HIV in Africa was initially hidden behind common infections and HIV first came to world awareness in focal areas of the USA as a disease seemingly limited to gay males. The epidemic of intravenous drug abuse in Edinburgh was associated with overlapping epidemics of bloodborne viruses like hepatitis B, hepatitis C and HIV.