Sure and if it had arisen in Europe then those questions would have to be asked. But it's a safe assumption that very little analysis is happening in southern central Africa. It doesn't seem that outrageous that a parallel line has been percolating there for quite some time and only recently gained a mutation or two that allowed it to shoot to stratospheric levels.

Even in Europe I wouldn't find it all that difficult to believe. We see the same sort of pattern, qualitatively speaking, even in well controlled in vitro experiments.