The disease has spread from Guinea to Liberia [2] so this would be a jump Eastward [3]
[1] http://www.npr.org/blogs/health/2014/06/25/324941229/could-t...
[2] http://en.wikipedia.org/wiki/2014_West_Africa_Ebola_outbreak...
[3] https://www.google.co.uk/maps/place/West+Africa/@14.6336215,...
I'm only aware of these cases (are there others?) Hence, I used theory until you've had a few more occurrences.
The first link in the previous comment documents:
1) 1996 a man in Gabon travelling to Johannesburg and he didn't infect anyone.
2) 2004, a man with Lassa fever, similar to Ebola, travelling to the US and not infecting anyone.
Not sure how to filter the non-2014 outbreaks, though.
All it takes is a single mistake, or one vector of transmission that was not yet known, or one patient sneezing at exactly the wrong moment or simply not having the tools and supplies to do the work safely.
Being a doctor in this field is a very high risk occupation, doing it in Africa is simply very brave.
For similar reasons, you'd expect the world's foremost expert on avoiding shark attacks to be attacked by a shark more often than the general population. He's out there practicing his theories and doing his research every day. The rest of us aren't going in the water as often.
The best way to avoid being attacked by a shark in the ocean is not to go in the ocean. The best way to avoid contracting Ebola is to stay as far away from Ebola as possible. An expert might be better able to handle himself around Ebola, or around sharks, than the rest of us. But he's also more likely to be around Ebola (or sharks) in the first place.