Why do totally dissimilar countries like Egypt, Mongolia, Japan, Slovakia, Bangeldash share a low HIV rate ?

They countires have virtualyl nothing in common other than a low HIV rate (less than a tenth of a percent in 2005) yet have nothing in common. Likewise nations as diverse Haiti, Russia, Angola, and Thailand have a high rate and the US, Somalia, Brazil, India, and Spain all share one around one percent. What sociological factors dictate this disease's reality ?