History

The issue of the origin of HIV could go beyond one of purely academic interest, as an understanding of where the virus originated and how it evolved could be crucial in developing a vaccine against HIV and more effective treatments in the future. Also, a knowledge of how the AIDS epidemic emerged could be important in both mapping the future course of the epidemic and developing effective education and prevention programme.

What type of virus is HIV?

HIV is part of a family or group of viruses called lentiviruses. Lentiviruses other than HIV have been found in a wide range of nonhuman primates. These other lentiviruses are known collectively as simian (monkey) viruses (SIV) where a subscript is used to denote their species of origin.

Where did HIV come from?

It is now generally accepted that HIV is a descendant of simian (monkey) immunodeficiency virus (SIV). Certain simian immunodeficiency viruses bear a very close resemblance to HIV-1 and HIV-2, the two types of HIV.

For example, HIV-2 corresponds to a simian immunodeficiency virus found in the sooty mangabey monkey (SIV_sm), sometimes known as the green monkey, which is indigenous to western Africa.

The more virulent strain of HIV, namely HIV-1, was until very recently more difficult to place. Until 1999 the closest counterpart that had been identified was the simian (monkey) immunodeficiency virus that was known to infect chimpanzees (SIV_cpz), but this virus had significant differences between it and HIV.

How could HIV have crossed species?

It has been known for a long time that certain viruses can pass from animals to humans, and this process is referred to as zoonosis.

The researchers from the University of Alabama have suggested that HIV could have crossed over from chimpanzees as a result of a human killing a chimp and eating it for food.

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

The journalist Edward Hooper has suggested that HIV could be traced to the testing of an oral polio vaccine called Chat as batches of the Chat vaccine may have been grown in chimp kidney cells in the Congo, the Wistar Institute and Belgium. That could have resulted in the contamination of the vaccine with chimp SIV, the simian version of HIV-1. This vaccine was then given to about a million people in the Belgian Congo, Ruanda and Urundi in the late 1950s.

However, in February 2000 the Wistar Institute in Philadelphia announced that it had discovered in its stores a phial of polio vaccine that had been used as part of this polio vaccination program. The vaccine was subsequently analysed and in April 2001 it was announced³ that no trace had been found of either HIV or chimpanzee. A second analysis⁴ confirmed that only macaque monkey kidney cells, which cannot be infected with SIV or HIV, were used to make Chat.

What is crucial in regard to the credibility of any theory is the question of when the transfer took place

What caused the epidemic to spread so suddenly?

There are a number of factors that may have contributed to the sudden spread including international travel, the blood industry, and widespread drug use.

The role of international travel in the spread of HIV was highlighted by the case of 'Patient Zero'. Patient Zero was a Canadian flight attendant called Gaetan Dugas who travelled extensively worldwide. Analysis of several of the early cases of AIDS showed that the infected individuals were either direct or indirect sexual contacts of the flight attendant. These cases could be traced to several different American cities demonstrating the role of international travel in spreading the virus. It also suggested that the disease was probably the consequence of a single transmissible agent.

As blood transfusions became a routine part of medical practice, this led to a growth of an industry around meeting this increased demand for blood. In some countries such as the USA paid donors were used, including intravenous drug users. This blood was then sent worldwide. Also, in the late 1960's haemophiliacs began to benefit from the blood clotting properties of a product called Factor VIII. However, to produce the coagulant, blood from thousands of individual donors had to be pooled. Factor VIII was then distributed worldwide making it likely that haemophiliacs could become exposed to new infections.

The 1970s saw an increase in the availability of heroin following the Vietnam War and other conflicts in the Middle East, which helped stimulate a growth in intravenous drug use. This increased availability together with the development of disposable plastic syringes and the establishment of 'shooting galleries' where people could buy drugs and rent equipment provided another route through which the virus could be passed on.

Early Growth of AIDS

Sources:
Avert website
Chart from Own words website