Incarceration in the United States is frequently described as an epidemic, with per capita rates nearly quadrupling in the past 30 years. African-Americans appear to be particularly susceptible: In 2011, they were six times more likely than whites to be incarcerated, making up 38% of the 1.6 million Americans behind bars while accounting for only 13% of the U.S. population. Now, a computer simulation originally developed to track infectious disease suggests the longer prison sentences that blacks often receive may accelerate the rate of “infection.”
http://news.sciencemag.org/biology/2014/06/prison-contagious