In the early 1980s, all at once “new” and “unusual” diseases began to generate an immune deficiency unseen before. As we very well know, this deficiency was not restricted to a single risk category. When reading the clinical reports dating from the 1980s, we can see that the cases were quite diverse with respect to gender, ethnic origin, age, geographic area, and habits. Yet this diversity was channeled and systematized into risk categories. The recognition of the new immune deficiency relied precisely on a classificatory system that would tie it to certain social categories. What was the economy of this system? Which resources did it use and how? What were the relationships between risk categories? How were they constituted with respect to one another? How did they shape knowledge of the causal agent and its transmission?

The Classification of Risks

The first risk categories with which the medical AIDS discourse operated were hardly new or unusual. The term “homosexuals” was established as a medical category at the end of the nineteenth century, occupying an important role in medical models of human sexuality (Conrad 1986; Conrad and Schneider 1985, pp. 181–5; Poirier 1988; Pressman 1990). It was presented both as a disease and as a medical condition liable to attract other diseases. In the 1970s, homosexuality was associated with (and held responsible for) the reemergence of sexually transmitted diseases, especially hepatitis B (Epstein 1988); it was thus seen more as a general condition favoring the appearance of infectious diseases than as a disease per se.