determine whether HIV is present in a blood or plasma sample

When?

During the last few years it has become possible not only to determine whether HIV is present in a blood or plasma sample, but also to determine the particular subtype of the virus. Studying the subtype of virus of some of the earliest known instances of HIV infection can help to provide clues about the time it first appeared in humans and its subsequent evolution.

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.¹¹
2. A lymph node sample taken in 1960 from an adult female, also from the Democratic Republic of the Congo.¹²
3. HIV found in tissue samples from an American teenager who died in St. Louis in 1969.¹³
4. HIV found in tissue samples from a Norwegian sailor who died around 1976.¹⁴

A 1998 analysis of the plasma sample from 1959 suggested that HIV-1 was introduced into humans around the 1940s or the early 1950s.¹⁵

In January 2000, the results of a new study¹⁶ suggested that the first case of HIV-1 infection occurred around 1931 in West Africa. This estimate (which had a 15 year margin of error) was based on a complex computer model of HIV's evolution.

However, a study in 2008¹⁷ dated the origin of HIV to between 1884 and 1924, much earlier than previous estimates. The researchers compared the viral sequence from 1959 (the oldest known HIV-1 specimen) to the newly discovered sequence from 1960. They found a significant genetic difference between them, demonstrating diversification of HIV-1 occurred long before the AIDS pandemic was recognised.

The authors suggest a long history of the virus in Africa and call Kinshasa the “epicentre of the HIV/AIDS pandemic” in West Africa. They propose the early spread of HIV was concurrent with the development of colonial cities, in which crowding of people increased opportunities for HIV transmission. If accurate, these findings imply that HIV existed before many scenarios (such as the OPV and conspiracy theories) suggest.

What about HIV-2? When did that get passed to humans?

Until recently, the origins of the HIV-2 virus had remained relatively unexplored. HIV-2 is thought to come from the SIV in Sooty Mangabeys rather than chimpanzees, but the crossover to humans is believed to have happened in a similar way (i.e. through the butchering and consumption of monkey meat). It is far rarer, significantly less infectious and progresses more slowly to AIDS than HIV-1. As a result, it infects far fewer people, and is mainly confined to a few countries in West Africa.

In May 2003, a group of Belgian researchers published a report¹⁸ in Proceedings of the National Academy of Science. By analysing samples of the two different subtypes of HIV-2 (A and B) taken from infected individuals and SIV samples taken from sooty mangabeys, Dr Vandamme concluded that subtype A had passed into humans around 1940 and subtype B in 1945 (plus or minus 16 years or so). Her team of researchers also discovered that the virus had originated in Guinea-Bissau and that its spread was most likely precipitated by the independence war that took place in the country between 1963 and 1974 (Guinea-Bissau is a former Portuguese colony). Her theory was backed up by the fact that the first European cases of HIV-2 were discovered among Portuguese veterans of the war, many of whom had received blood transfusions or unsterile injections following injury, or had possibly had relationships with local women.