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Thursday, 2 June 2011

The Origin of HIV

The origin of AIDS and HIV has puzzled scientists ever since the illness first came to light in the early 1980s. For over twenty years it has been the subject of fierce debate and the cause of countless arguments, with everything from a promiscuous flight attendant to a suspect vaccine programme being blamed. So what is the truth? Just where did AIDS come from?
The first recognised cases of AIDS occurred in the USA in the early 1980s (more about this period can be found on our History of AIDS page). A number of gay men in New York and California suddenly began to develop rare opportunistic infections and cancers that seemed stubbornly resistant to any treatment. At this time, AIDS did not yet have a name, but it quickly became obvious that all the men were suffering from a common syndrome.
The discovery of HIV, the Human Immunodeficiency Virus, was made soon after. While some were initially resistant to acknowledge the connection (and indeed some remain so today), there is now clear evidence to prove that HIV causes AIDS. So, in order to find the source of AIDS, it is necessary to look for the origin of HIV, and find out how, when and where HIV first began to cause disease in humans.


The 'hunter' theory

 The most commonly accepted theory is that of the 'hunter'. In this scenario, SIVcpz 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 became 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.

An article published in The Lancet in 2004, also shows how retroviral transfer from primates to hunters is still occurring even today. In a sample of 1099 individuals in Cameroon , they discovered ten (1%) were infected with SFV (Simian Foamy Virus), an illness which, like SIV, was previously thought only to infect primates. All these infections were believed to have been acquired through the butchering and consumption of monkey and ape meat. Discoveries such as this have led to calls for an outright ban on bushmeat hunting to prevent simian viruses being passed to humans.

The oral polio vaccine (OPV) theory

 Some other rather controversial theories have contended that HIV was transferred iatrogenically (i.e. via medical interventions). One particularly well-publicised idea is that polio vaccines played a role in the transfer.

In his book, The River, the journalist Edward Hooper suggests that HIV can be traced to the testing of an oral polio vaccine called Chat, given to about a million people in the Belgian Congo, Ruanda and Urundi in the late 1950s. To be reproduced, live polio vaccine needs to be cultivated in living tissue, and Hooper's belief is that Chat was grown in kidney cells taken from local chimps infected with SIVcmz. This, he claims, would have resulted in the contamination of the vaccine with chimp SIV, and a large number of people subsequently becoming infected with HIV-1.

Many people have contested Hooper's theories and insist that local chimps were not infected with a strain of SIVcmz that is closely linked to HIV. Furthermore, the oral administration of the vaccine would seem insufficient to cause infection in most people (SIV/HIV needs to get directly into the bloodstream to cause infection - the lining of the mouth and throat generally act as good barriers to the virus).6 

In February 2000 the Wistar Institute in Philadelphia (one of the original manufacturers of the Chat vaccine) announced that it had discovered in its stores a phial of polio vaccine that had been used as part of the program. The vaccine was subsequently analysed and in April 2001 it was announced that no trace had been found of either HIV or chimpanzee SIV.A second analysis confirmed that only macaque monkey kidney cells, which cannot be infected with SIV or HIV, were used to make Chat. While this is just one phial of many, it means that the OPV theory remains unproven.The fact that the OPV theory accounts for just one (group M) of several different groups of HIV also suggests that transferral must have happened in other ways too, as does the fact that HIV seems to have existed in humans before the vaccine trials were ever carried out.

The contaminated needle theory 

The colonialism or 'Heart of Darkness' theory, is one of the more recent theories to have entered into the debate. It is again based on the basic 'hunter' premise, but more thoroughly explains how this original infection could have led to an epidemic. It was first proposed in 2000 by Jim Moore, an American specialist in primate behaviour, who published his findings in the journal AIDS Research and Human Retroviruses.

During the late 19th and early 20th century, much of Africa was ruled by colonial forces. In areas such as French Equatorial Africa and the Belgian Congo, colonial rule was particularly harsh and many Africans were forced into labour camps where sanitation was poor, food was scarce and physical demands were extreme. These factors alone would have been sufficient to create poor health in anyone, so SIV could easily have infiltrated the labour force and taken advantage of their weakened immune systems to become HIV. A stray and perhaps sick chimpanzee with SIV would have made a welcome extra source of food for the workers. 

“SIV could easily have infiltrated the labour force and taken advantage of their weakened immune systems”

Moore also believes that many of the labourers would have been inoculated with unsterile needles against diseases such as smallpox (to keep them alive and working), and that many of the camps actively employed prostitutes to keep the workers happy, creating numerous possibilities for onward transmission. A large number of labourers would have died before they even developed the first symptoms of AIDS, and those that did get sick would not have stood out as any different in an already disease-ridden population. Even if they had been identified, all evidence (including medical records) that the camps existed was destroyed to cover up the fact that a staggering 50% of the local population were wiped out there.

One final factor Moore uses to support his theory, is the fact that the labour camps were set up around the time that HIV was first believed to have passed into humans - the early part of the 20th century.

The conspiracy theory 

Some say that HIV is a 'conspiracy theory' or that it is 'man-made'. A recent survey carried out in the US for example, identified a significant number of African Americans who believe HIV was manufactured as part of a biological warfare programme, designed to wipe out large numbers of black and homosexual people. Many say this was done under the auspices of the US federal 'Special Cancer Virus Program' (SCVP), possibly with the help of the CIA. Linked in to this theory is the belief that the virus was spread (either deliberately or inadvertently) to thousands of people all over the world through the smallpox inoculation programme, or to gay men through Hepatitis B vaccine trials. While none of these theories can be definitively disproved, the evidence given to back them up is usually based upon supposition and speculation, and ignores the clear link between SIV and HIV or the fact that the virus has been identified in people as far back as 1959.