Let's take your table and overlay some additional figures on it, namely percentage of population that is Christian and Muslim.
It would appear that rates of HIV are highest in countries that are dominated by primarily Christian populaces. If your generalization that HIV rates are highest in the south of Africa holds true, which I see no reason to doubt you on, one notices the curious correlation that HIV rates are highest in the Christian dominated countries in the south of Africa, and less so in the Muslim dominated northern countries. ("Things that make you go, hmmm....") A rough figure is that the average is 40% Muslim and 47% Christian for Africa as a whole. It would appear that Christianity is highly compatible with behavioral practices which lead to HIV infection.
See Wikipedia: Religion In Africa, Wikipedia: Christianity By Country (especially the demographic world map), and Wikipedia: Islam By Country (also for its demographic world map) for more information. See also the epidemiological maps of HIV infection (estimated) globally at Wikipedia: ; it appears the pattern of incidence in the south has shifted in composition, but it's still greater in the south than the north.