ABSTRACT
Injecting drug users (IDUs) become infected with HIV in a limited number of ways: by sharing syringes or other paraphernalia in direct interactions with others; by injecting drugs with contaminated injection equipment previously used by unknown IDUs at shooting galleries, dealer houses, abandoned buildings, or at outside locations (Marmor et al., 1987; Schoenbaum et al., 1989); by having the drug mixture for two or more IDUs prepared for injection in a previously used syringe (Jose et al., 1993); or by unprotected sex. In all of these patterns except when sharing contaminated equipment used by unknown IDUs, risk behaviour involves direct social interaction between two or more individuals and therefore allows for social pressure to come into play. Even in situations where direct social interaction between IDUs does not occur, the sharing of injection equipment is influenced by the dynamics of core institutions of the drug subculture such as various indoor or outdoor gathering places where drugs and equipment are bought and/or used by a number of IDUs (perhaps from different friendship groups). Normative and other pressures also occur in these settings. Ethnographic studies have provided a detailed picture of the complexity of these interactions (McKeganey and Barnard, 1992; Grund, 1993).
