Problem with 'sharp doctor in Africa' is that health care sucks there. If millions of people are suffering from malaria and TB and lots of other diseases, and also malnutrition etc., AND have few medical records, it becomes much, much harder to find a rare or new disease, especially one that doesn't kill people directly (when there's so much other stuff going on).
In the US it was found because a doctor found a cluster of Karposi's Sarcoma, which normally is a really, really rare disease, and went looking. It was the good level of general healthcare in the US that allowed the signal to be visible above the noise of the general ill health.
Besides, the labs and testing facilities available in much of Africa are minimal in many places and overworked everywhere.
In the US it was found because a doctor found a cluster of Karposi's Sarcoma, which normally is a really, really rare disease, and went looking. It was the good level of general healthcare in the US that allowed the signal to be visible above the noise of the general ill health.
Besides, the labs and testing facilities available in much of Africa are minimal in many places and overworked everywhere.