“…Urban populations may be more likely to have access to illicit drugs and to engage in injection drug use (McCurdy, Williams, Kilonzo, Ross, & Leshabari, 2005;Wodak, Sarkar, & Mesquita, 2004). Drug injection behaviors have been known to facilitate the transmission of HIV since the epidemic was first recognized (Blattner, O'Brien, & Mueller, 1997). In a number of cities around the world, drug injection practices, particularly the sharing of needles used for injecting heroin, have strongly influenced local epidemics (Chaisson, Bacchetti, Osmond, Brodie, & Sande, 1989;Davies, Dominy, Peters, & Richardson, 1996;Des Jarlais, 1992;Friedman, Jose, Deren, Des Jarlais, & Neaigus, 1995;Vanichseni et al, 1992Vanichseni et al, , 1993Wodak, Stowe, Ross, Gold, & Miller, 1995).…”