"Was polio vaccine the cause of AIDS?"

(Review of The River: A Journey Back to the Source of HIV and AIDS)

Bill Hamilton, the brilliant Oxford zoologist who died last week, caught his fatal disease while in the Congo. He was there in search of chimpanzee stools with which to test a radical theory about the origin of the AIDS virus. Saddened by his death, I spent the weekend reading the book that had convinced him of this theory. It has shaken me to the core.

The book is 'The River' by Edward Hooper (Penguin, £25). More than a thousand pages long and nine years in preparation it is quite unlike what I expected: fair, cautious and thorough. Hooper gradually came to the conclusion that although none of the fanciful theories about the origin of AIDS (from the CIA to extraterrestrials) were right, nor was the conventional explanation. This holds that the virus occasionally jumped from chimpanzee to human being via a bite or scratch, but only turned epidemic when roads and urbanisation opened up central Africa and altered sexual habits there.

Instead, Hooper doggedly pursues the evidence that a much more sinister explanation holds: the virus jumped from primates into the human species via one or more contaminated batches of the live polio vaccine that was being experimentally tested in Africa in the late 1950s. Such polio vaccines are generally grown in monkey tissue and have sometimes been contaminated with other monkey viruses.

This theory accounts for things that the conventional theory cannot explain such as the close family tree of the main strain of human AIDS virus, implying a late 1950s origin, and the simultaneous appearance in the 1960s of three different types of HIV, coincident with three areas where the polio vaccine trials happened in the late 1950s. The explosion of HIV infection in rural western Burundi long before its appearance elsewhere in the continent happened in the very villages where a large trial of a polio vaccine was done in 1958.

Hooper admits his case is not proven, though this is largely because the Wistar Institute in Philadelphia has not released tests of the vaccine seed stock it holds in cold storage. Three Swedish samples of the relevant vaccine have proved negative, but the Swedes have oddly refused to test what species of primate was used to make the vaccines despite Hooper's and Hamilton's requests. There remains a strong suspicion that they were made from chimpanzees, hundreds of which were sacrificed at a medical facility near Kisangani in Congo at the right time. Hamilton was collecting the stools of chimpanzees from around Kisangani to test whether they carry the 'M' strain of HIV, which has caused the main global pandemic. If they do, the case is very strong indeed.

The polio theory will be discussed at a two-day meeting of the Royal Society in May. So far it has received a hostile reaction from much of the medical profession, which is understandable. Vaccination does immense good and any contamination is long in the past. To somebody like me who believes that medicine and biotechnology are overwhelmingly forces for good, it is painful even to publicise a theory that dents that confidence.

None the less, if Hooper is right - and he has definitely put the burden of proof on his critics - the implications are dreadful. It means that the last legacy of colonialism includes quite literally a plague that has killed 16 million Africans and lowered life expectancy all across the continent.

It is not the only disease outbreak possibly linked with 'iatrogenic' (doctor-caused) origins. The near-lethal Ebola virus does seem to jump quite naturally into people, but its first outbreaks into serious epidemics happened in clinics and hospitals where it was spread by well meaning nurses with re-used syringe needles.

Much more controversially - and probably wrongly - it has also been suggested in evidence to the BSE inquiry that the new outbreak of human vCJD just might have been caused by the use of bovine serum for the preparation of vaccines and other medicines, rather than by eating beef. This hypothesis was rapidly rejected by the early inquiries into BSE, but partly, it seems, because the implications would be too alarming in terms of undermining trust in the medical profession-a consideration that was not extended to the farming profession.