The Cruellest Irony: We May Have To Think the Unthinkable About HIV and AIDS
Could doctors testing a polio vaccine in Africa in the late 1950s have unintentionally started the AIDS epidemic?
Seven years after this conspiracy-style theory was first floated, the publication of The River, a new book by the writer Edward Hooper, is forcing scientists to take this disturbing possibility seriously again. Hooper spent nine years researching the book and has paid great attention to detail. Few experts doubt that he has done his homework. So how seriously should we take the theory?
It's widely accepted that humans became infected with HIV-1, the main AIDS virus, through contact with chimpanzees. When and how the chimp version of the virus jumped into humans, however, is much less clear. Epidemiologists' best guess is that hunters became infected with blood as they cut up chimp carcasses for meat.
By contrast, Hooper's theory centres on a polio vaccine that was tested on about a million people in central Africa between 1957 and 1960. Because the vaccine was produced in cultures of kidney cells from various primate species, Hooper argues that some of it could have been contaminated with the virus that was later identified in humans as HIV-1. All that was needed to seed the AIDS epidemic was a few contaminated batches.
If Hooper is right, it would mean 14 million people have so far died and 33 million been infected because of a well-intentioned--and ultimately successful--attempt to stem the tide of polio. That's some tragic irony. But discomfort is no reason to ignore the possibility.
When the vaccine theory of AIDS first surfaced, scientists could be justifiably dismissive. The word then was that the kidney cells used to make the polio vaccines came from macaque monkeys, not chimps. Also, scientists believed that the first recognisable case of AIDS involved a British seaman whose travels were over before the vaccinations began.
We now know that this was not a genuine HIV infection. More importantly, Hooper provides the first evidence that chimp kidneys may have been used to culture the vaccine and he identifies a geographic match between the vaccine trial sites and what are now regarded as the first known cases of HIV infection, including the earliest in 1959.
But if the vaccine theory has become less obviously far-fetched, it still has problems. For example, the vaccine was also tested on thousands of individuals in Poland but there's no evidence of early HIV infection there. Secondly, different subspecies carry different forms of the chimp virus and, if current research is correct, the subspecies of chimp from the Congo whose kidneys might have been used is the "wrong" one: it harbours only a distant relative of HIV-1.
And if vaccine trials were responsible for HIV-1 in central Africa, where does that leave HIV-2, the sister virus that emerged in West Africa? HIV-2 seems to have "jumped" species from the sooty mangabey in at least four separate incidents. Were vaccines involved in these leaps too? Or did HIV-1 need help to jump species even though HIV-2 didn't? Either version requires excessive special pleading. Especially since biologists who have studied different strains of HIV-1 are confident that they began to diverge from a single viral ancestor no later than 1940.
But even if there is only the tiniest chance that Hooper is right, the implications of his theory demand that it should be investigated. The obvious next step is to test the remaining frozen stocks of the vaccine for the presence of the chimp virus. Of course, negative results will not resolve the controversy, because other batches, now used up or lost, might have been contaminated. But this is no excuse for doing nothing.
So far, few of the players have shown any sense of urgency. An expert committee that looked into the vaccine theory in 1992 called for tests on the remaining stocks and an end to using monkey tissues to make vaccines. Well, the stocks have still not been tested, and although most manufacturers have switched to using human cells to culture the vaccine, some still have not. Production methods are far more stringent than they were 40 years ago. But the fact is that any vaccines cultured in monkey tissues could still carry a risk of unknown primate viruses.
For this and other reasons, it is now up to the WHO to try to answer Hooper's questions as quickly as possible. A refusal to test the leftover vaccine stocks will simply fuel conspiracy theories everywhere.
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