ABSTRACT
In this paper, we discuss two diseases (or, in the case of AIDS, clusters of disease) which appear at first glance to fall into the clear cut category of viral etiology, with transmission by intimate contact between persons, or via blood. This is contagion facilitated by what has been termed ‘risk groups’ and subsequently ‘risk behaviour’. For this form of transmission, we use the term ‘horizontal risk’ because such contagion passes sideways, as it were, mainly between consenting, or ignorant, adults. There is no doubt about the nature of this horizontal contagion for both hepatitis B and for AIDS. But where does the issue of heredity emerge? Initially we could think of no hereditary element in the framing of the two diseases syndromes. But familiarity with their histories enabled us to recognise ways in which other framings co-existed with the horizontal viral-contagion model. These are what we have termed the ‘vertical ancestries’ in this paper.
