Bad blood and good intentions

Could the Aids epidemic have its origins in polio vaccinations in the Congo in the 1950s? Robert Trivers considers a persuasive argument.

Many Africans and African-Americans believe that HIV and Aids were either the direct invention of the white man - cooked up, for example, in the biological warfare labs in Fort Detrick, Maryland - or somehow preferentially directed at them by wicked, white scientists. A book by Edward Hooper suggests that something like this may actually have happened, that the Aids epidemic may have started when HIV was accidentally introduced into hundreds and perhaps thousands of Africans during vaccinations of more than 1 million people, mostly children, against polio in 1958 and 1959 in Rwanda-Burundi and selected places in the Congo.

In a masterful account of the early history of HIV infection and Aids, Hooper shows that HIV first jumped to substantial heights in human populations in exactly those sections of these countries in which large-scale polio vaccinations took place 20 years before. This naturally makes one wonder whether the two events were related. The most plausible connection - and the one pursued by Hooper - is that the live polio vaccine, administered orally, was contaminated with the HIV virus (or, technically, the chimpanzee's HIV, called SIV) so that a small fraction of those taking the vaccine may also - through oral lesions, for example - have taken up an HIV infection. Since more than 1 million Africans were vaccinated, the fraction would not have to be high (say, 1 in 1,000) to produce a substantial seed population (1,000 infected individuals) with which to begin a worldwide epidemic. This theory is known as the oral polio vaccine HIV theory, or OPV-HIV theory for short.

The alternative theory is that we contracted HIV from the chimpanzee SIV either by eating undercooked infected chimpanzees or by accidental transfer during killing, skinning or keeping them as pets. This theory has the advantage that repeated such events must have been occurring over a long period of time. The disadvantage is that the infection starts at a very low frequency - one or a few individuals - and is likely on statistical grounds alone to go extinct in each case before an adaptively evolving parasite can successfully be launched into hundreds and then thousands of humans. As for the early appearance of the epidemic, this theory suggests no particular time but does suggest areas of Africa where chimp hunting and eating were common, which are not the precise sections of Africa in which HIV actually came to numerical prominence.

The OPV-HIV theory for the introduction of HIV into humans suffers from the lack of any direct evidence that chimpanzee tissue was used to culture the polio vaccines. To be sure, the chief vaccinator, Hilary Kropowski, kept a huge chimpanzee colony in the Congo, far larger than needed to test the attenuated virus (for possible crippling effects) and he was known to have sent chimpanzee kidneys back to Philadelphia for other kinds of work. Kropowski and the few remaining survivors (among the scientists) of this vaccinationdeny that chimpanzee tissue was ever used to culture the polio virus, but there are several problems with Kropowski's denial. He vaccinated more than a million human beings without ever publishing the protocol by which the vaccine was generated. This violates the most fundamental tenet of science, that any and all experiments and observations are described in such a way that they can be repeated exactly by others, the better to test their verisimilitude.

Kropowski's singular failure to document his mass experiment is compounded by his subsequent loss - so he informs us - of all of his research records for the period in question. In addition, as Hooper ably shows, when Kropowski did publish protocols for his work, he sometimes had the habit of publishing the penultimate protocol instead of the current one. That is, if in earlier work he cultured the polio virus in chick embryo cells but now did so in monkey kidney cells as well, he states that he is still using only chick embryo cells - as if waiting for any adverse results before admitting to the new protocol. Although samples of the original vaccine exist frozen in the Wistar Institute of Philadelphia, the institute and Kropowski (its former director) have refused until recently to permit these samples to be tested for the presence of chimp SIV (and also chimp mitochondrial DNA).

The River is filled with fascinating detective work and acute characterisations of the human actors. For example, Hooper captures the famously self-serving US virologist Robert Gallo in a few deft strokes: he "strode toward us, his hand already extended in greeting. 'Now why do I get the feeling,' he inquired with an easy smile, 'that you and I are going to get along?'" Why, indeed? I only part company with Hooper when he interprets the kind of scientific misbehaviour he describes as providing much support for the OPV-HIV theory. It certainly is consistent with the theory but it is consistent with many other possibilities. For all we know, Kropowski grew his polio virus in crushed orangutan testicles and is embarrassed now to admit it, or he did grow it in chimpanzee tissue but none was infected with SIV, and so on. But even with all documentation lost, we should not underestimate the ability of science to probe the past. Some fascinating evidence is now emerging from molecular biology (HIV may be a recombinant virus, primarily but not exclusively of chimpanzee origin) and intensive study of chimpanzees and other central African primates will undoubtedly prove informative.

That undocumented - or poorly documented - mass experiments on humans are still common is suggested by Gulf war syndrome. Pentagon records are so shoddy that it may never be known which soldiers took which drugs in which combinations, but that these drugs had serious and enduring side-effects for 100,000 soldiers seems all but certain. One good candidate at the moment is pyridostigmine bromide, used as a "pretreatment" for possible attacks with the nerve agent Soman. The bromide is now known to cause nerve damage in animals, especially when combined with other drugs, such as vaccines, which themselves are known sometimes to induce auto-immune disease in humans. Yet medical personnel blithely run these mass experiments, assuring all that dangers are minimal, then denying the very real negative effects and, finally, crying lack of evidence, since they did not bother to keep the proper records by which such a disaster could later be analysed and ameliorated. A hard-hitting foreword to the book by W. D. Hamilton - probably the greatest evolutionary thinker of the 20th century - warns against "xenotransplants" in general, ie transfers of living tissue from other species into humans - pig heart valves being the latest craze. The problem is that you do not know what other species, ie parasites, you are also transplanting.

Apart from the main argument, Hooper's definitive account of the early spread of HIV provides many fascinating insights and/or speculations. For example, why Haitians? They were among the original "4 Hs", the other three of which we understand because HIV will gain easy access from others: homosexuals (via anal intercourse), haemophiliacs (via blood transfusions) and heroin users (via shared needles). But why Haitians? Hooper points out that some middle-class Haitians worked in French-speaking sections of Africa, such as the Congo, in the 1950s when a need arose for middle-class dark-skinned workers in these countries. The men would have had ready access to many women in Africa and, in turn, many women when they returned home.

Hooper's research suggests that Idi Amin's final goodbye present to East Africa may have been the hastening of the HIV epidemic into both Uganda and Tanzania. When he seized a small section of Tanzania in 1979, President Nyerere decided he had had enough of Amin, drove the Ugandan army out of the seized territory and then marched into Kampala to liberate Uganda. But the problem is that the Tanzanian army camped for nearly a year in and near the seized land and had ready access to a town that was a smuggling centre across Lake Victoria and which harboured many prostitutes and other young women, whom the Tanzanian soldiers may be assumed to have taken to enthusiastically. This zone was an early area of high HIV infection, and Hooper speculates that the Tanzanian army brought HIV in large numbers into Kampala and then brought it home with them when they returned to Dar es Salaam.

Hooper's book makes OPV-HIV the theory to beat. In the process of solving this puzzle we will undoubtedly get a much deeper understanding of the myriad ways in which white people, inadvertently or otherwise, may have helped launch plagues on the great African continent.

Robert Trivers is professor of anthropology and biological sciences, Rutgers University, New Jersey, United States.