AIDS: Science at a Crossroads

This is not an outlandish idea: many viruses and bacteria "jump" species. For example, influenza
viruses are thought to originate in domestic fowl and spread to pigs before they are transmitted to
humans. Many virologists have argued that a forerunner of HIV could have "jumped" species from
monkeys to humans if blood from a monkey was splashed into a cut or a mucous membrane, such as
the eye. In communities where monkey meat is eaten and where monkeys are often kept as pets, this
scenario is plausible. Strains of the HIV-related simian immunodeficiency virus (SIV) have been found
in macaques, mangabeys, mandrills and vervets. A number of scientists such as Dr Gerald Myers of the
Los Alamos National Laboratory HIV Database in New Mexico, US, have discussed the origins of the
virus but have not been able to do more than speculate.
There are in fact two distinct human immunodeficiency viruses: HIV-1, which is widespread around
the world: and HIV-2, a less virulent form which has been mainly confined to West Africa with a few
cases of infection elsewhere. HIV-2 is genetically similar to certain strains of SIV found in captive
macaques. HIV-1, however, is genetically distant from SIV and HIV-2. HIV-1 's closest relatives have
been found in a very small number of chimpanzees from central and West African countries, but the
samples of virus from these animals are still being analysed. It seems probable that HIV-1 and HIV-2
"jumped" species separately and have separate ancestors.
But no one knows exactly when either virus first entered the human population. Until recently,
scientists believed that they had found the earliest clear, documented case of HIV infection in a British
sailor who died in 1959 of a wasting disease and whose stored tissues were reported to be infected with
HIV. However, this case is now in serious doubt. Whatever the outcome, there is no evidence of
widespread HIV infection before the mid to late 1970s, anywhere in the world.
The most plausible theory is that HIV entered the human population sometime in the past - maybe as
recently as the 1970s but certainly within the last 100 years - and then remained isolated in a small
or remote group who may not have been severely affected by it. Wherever the virus originated, its
explosive spread began only in the 1970s when urbanisation, cheap travel and major international
conflict increased the potential for people from different communities to have sex with each other.
There have been claims of an isolated case of HIV infection in 1959 in Kinshasa (then Leopoldville),
Zaire. But contrary to popular opinion, there is no evidence of widespread HIV infection in Zaire or
anywhere else in sub-Saharan Africa before the mid to late 1970s. Successive testing of stored tissues
and blood samples from the 1950s and 1960s has failed to find any HIV infection (4). Claims by
Western journalists that AIDS is just a new name for an old disease long prevalent in sub-Saharan
Africa have irritated doctors and others in Africa who recognised it as something new and different (5).
Each time the virus makes copies of itself within the cells of an infected person, it makes errors in its
genetic material. Over time, therefore, it changes its genetic makeup significantly and develops
different variants (see page 3). By 1995, researchers had identified eight broad genetic strains (or
subtypes) of HIV-1 around the world, labelled A to H, all of which belong to a group the researchers
call "M".
In North America, a strain of HIV called subtype B is prevalent but in other populations, including
those of the former Soviet Union, much of sub-Saharan Africa and Brazil, several subtypes coexist (6).
There is also a different group known as the "O" group, genetically very different and identified so far
only in Gabon, Cameroon and France.
Polio vaccine exonerated
There are many popular alternative theories of the origin of AIDS, including some that are less
outlandish than the germ-warfare or space-alien theories. None, however, is supported by evidence.
One that seemed plausible at first glance was the suggestion that a monkey virus and forerunner of HIV
contaminated the first batches of a polio vaccine that was tested in the Congo and Zaire in the late

1950s. Monkey kidney cells were used to culture the poliovirus used in the vaccine.
However, this theory was effectively discounted by a committee of experts, chaired by Dr David Ho of
the Aaron Diamond AIDS Research Center in New York in 1992. There are several reasons why the

7- Panos Briefing: AIDS: SCIENCE AT A CROSSROADS