HIV Digest	HIV Digest Archive

The origins of HIV, and the date when simian immunodeficiency viruses (SIVs) crossed over to humans are still being studied. A recent study used phylogenetic analysis to estimate the year of HIV's origin. Researchers note that by the 1980s, when HIV was identified, widespread epidemics were already taking place. It was known that HIV-1 came from chimpanzees and viruses transmitted from sooty mangabeys were called HIV-2.

Scientists calculated that the best estimate for placing the common ancestry of HIV-1 M group is 1931. The designation of the early 1930s reveals that the virus must have been transmitted to humans before then, possibly in the 1800s or early 1900s. It is also possible that the virus infected humans around 1930 and rapidly began to spread. Another theory is that multiple strains of HIV jumped from chimpanzees to humans around the same time in the 1940s or 1950s.

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The new data seems to best support the Transmission Early theory. Under this concept, the spread of the virus was slow, since HIV was present in the 1930s but did AIDS did not become widespread until the 1970s. Scientists note that the epidemic exploded in the 1950s and 1960s, coincident with the end of colonial rule in Africa, several wars, the introduction of widespread vaccination programs (with the deliberate or inadvertent reuse of needles), the growth of large African cities, the sexual revolution, and increased travel by humans to and from Africa."

Editor's Note: from Science