The real problem with Ebola is that it leverages the immune response to enter the blood stream. So the immune system has to be strong but not hyperactive.
Good points.
I don’t know a thing about viruses, but anyone living in these places would probably be the descendant of people who had been exposed to this one or a similar one and survived, which might make them a little more resistant; or they might, as you say, be so weakened by other infections (Africa is nothing but a seething petri dish of viruses, fungus infections, parasites, etc.) that the ebola exposure is the last straw and their bodies can’t hold out.
That said, I hope we never have to find out how American and European bodies will react to it on a large scale.