Sociological approaches to the social control of sickness have tended to focus on medicalization or the process through which social phenomena come to be regulated by medicine. Much less is known about how social problems historically understood as medical come to be governed by the criminal law, or what I term the "criminalization of sickness." Thirty three US states have enacted criminal statutes that require all HIV-positive individuals to disclose their infection before engaging in a wide range of sexual practices. Drawing on evidence from 58 felony nondisclosure convictions in Michigan (95% of all convictions between 1992 and 2010), I argue that the enforcement of the state's HIV disclosure law is not driven by medical concerns or public health considerations. Rather, it reflects pervasive moralizing narratives that frame HIV as a moral infection requiring interdiction and punishment.