The most commonly accepted theory for the origin of AIDS is that of the 'hunter'. In this scenario, SIV (Simian Immunodeficiency Virus) was transferred to humans as a result of chimps being killed and eaten or their blood getting into cuts or wounds on the hunter. Normally the hunter's body would have fought off SIV, but on a few occasions it adapted itself within its new human host and become HIV-1. The fact that there were several different early strains of HIV, each with a slightly different genetic make-up (the most common of which was HIV-1 group M), would support this theory: every time it passed from a chimpanzee to a man, it would have developed in a slightly different way within his body, and thus produced a slightly different strain.

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Four of the earliest known instances of HIV infection are as follows:

1. A plasma sample taken in 1959 from an adult male living in what is now the Democratic Republic of the Congo.
2. A lymph node sample taken in 1960 from an adult female, also from the Democratic Republic of the Congo.
3. HIV found in tissue samples from an American teenager who died in St. Louis in 1969.
4. HIV found in tissue samples from a Norwegian sailor who died around 1976.

A 1998 analysis of the plasma sample from 1959 suggested that HIV-1 was introduced into humans around the 1940s or the early 1950s.

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It is likely that we will never know who the first person was to be infected with HIV, or exactly how it spread from that initial person. Scientists investigating the possibilities often become very attached to their individual 'pet' theories and insist that theirs is the only true answer, but the spread of AIDS could quite conceivably have been induced by a combination of many different events. Whether through injections, travel, wars, colonial practices or genetic engineering, the realities of the 20th Century have undoubtedly had a major role to play. Nevertheless, perhaps a more pressing concern for scientists today should not be how the AIDS epidemic originated, but how those it affects can be treated, how the further spread of HIV can be prevented and how the world can change to ensure a similar pandemic never occurs again.

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IF, indeed, homosexual men are the primary vector in the transmission of HIV (the truth of which is controversial at best), it would seem that one major step that would reduce the spread of the virus would be to discourage promiscuity and promote stable relationships by encouraging the passage of same-sex marriage bills.

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Side question:

The first outbreak (of Ebola hemorrhagic fever) took place on August 26, 1976, in Yambuku, a town in the north of what was then called Zaïre. The first recorded case was Mabalo Lokela, a 44-year-old schoolteacher returning from a trip around the north of the state.

Why, then, is Ebola hemorrhagic fever not refered to as "the schoolteacher's disease?"

Don Firth