What makes you think its going to take over the entire world, just because its spreading in the less educated countries. There is a cure for aids, but it requires treatment over a long period of time, which many of these countries can't afford/don't know about/can't reach/whatnot. It cannot spread in educated countries, even though cases certainly excises. It is also illegal in most countries to have sex if you have HIV, unless your partner knows about it. And lets be honest, good luck getting a partner with that.
And this is, lets be honest, a very low amount of things the government can do should it be any danger of a real spreadage in any civilized countries. Everything from exportion, contamination zones, criminalize HIV patients and/or force them for treatment are some of the few possibilities. Extermination is, lets be honest, not very ethical, and no countries would ever get behind that. Most likely, the country who went through with this would be condemned from the rest of the world, possibly even attacked. And I don't care what country it is, every country needs to trade.