South Africa's economy thrives despite shadow of AIDS

I find this report absolutely mystifying. If there's one thing we all know, not just from Sim economy-type games (my favorite is Pharoah), but from life, it's that nobody can do productive work when they are ill. How can SA go humming along in this condition? I don't think that the article really gets to the bottom of this question.

... off. But today, despite the adult population's estimated 20 percent HIV infection rate, the South African economy is flourishing. ...

Link: South Africa's economy thrives despite shadow of AIDS