Nearly 2% of the U.S. prison population has HIV, compared with 0.3% (or 1 million) of the total American population. But this is also a global problem: prisons in Brazil and Argentina have HIV infection rates over 4% — with some as high as 20% — and Eastern European countries such as Russia and Estonia report rates of 5%, according to the World Health Organization.

Stay tuned for more on World AIDS Day on Healthland coming up.