It’s only exponential if it spreads, yet it didn’t spread far over the decades of Ebola outbreaks, that over almost 40 years has led to deaths in the thousands, not millions.
What is your rough guess of millions for the American death toll? How about Europe and the orient?
You are already predicting millions of African dead, what about the rest of the world?
Unless a cure is found (unlikely) or unless it evolves to where it's not a threat then a realistic number is that it will stop when it runs though humanity and/or can't reach anymore humans. If it runs through humanity it will kill a certain percentage of people it infects (right now averaging around 70%), a certain percentage will be naturally immune and a certain percentage will never be exposed before the virus dies off. So if I had to make a guess I would say it could kill up to a 1/3 of the earths population.
The only other thing that could stop it right now is to completely cut off those countries where it's out of control. Even that is dicey though...it would have to be very strict....like shoot people trying to leave strict.