"The percentage of jail inmates reporting that they were HIV positive varied by level of prior drug use. Of jail inmates who reported never using drugs, 0.4% were HIV positive. An estimated 1.5% of inmates who had ever used drugs, 1.5% of those who used drugs in the month before their current offense, 3.2% of those who had used a needle to inject drugs, and 7.5% of those who had shared a needle reported being HIV positive."
Source
Maruschak, Laura M, HIV In Prisons and Jails, 2002, NCJ-205333, Washington, DC: Department of Justice, Bureau of Justice Statistics, Dec. 2004.