The percentage of people living with HIV is higher in poor and ecologically poor areas. For those of you interested in these issues, check out Gapminder's freely shared Adobe Flash presentation (download here) on HIV, which has static and animated graphs showing the relationship between the percentage of people living with HIV and income per person, and the actual number of people living with HIV. The data in the presentation shows how the HIV epidemic has changed in different countries between the years 1983 and 2007.
If you don't want to download the whole Flash slide show, Gapminder also provides an interactive and animated web-based graph of the data here. You can select one or more countries to see how HIV-prevalence has increased or decreased over time.