The only logical reason seems to be that their so-called 'Aids' illnesses - diarrhoea, TB and skin infections - were treated intensively and effectively with Western medicines. The villagers were promised these medicines, should they test HIV-positive, as an inducement to take part in the study. Such treatment is rarely available to the population at large.
The finding was part of a body of evidence that led the study organisers, after four years' work aided by 230 full-time staff in a province said to be an 'epicentre' of Aids, to drop their previous passionately held belief that HIV causes Aids, and to conclude that 'when you are here, and you have to witness the reality of what happens in the field, you cannot agree with any of the statements they are making in Europe about Aids in Africa'.
In some other African countries there is such a panic over HIV that many hospitals now tell patients who test positive to 'go home and die', one of a number of ill-effects that led Dr Timothy Stamps, Zimbabwe's minister of health and child welfare, to tell us that 'the HIV industry . . . is now in my view one of the biggest threats to health'.