One thing that is important to know is that there actually are not any confirmed cases in Sierra Leone [1] or Mali. There were many suspected cases in both countries, but all of them have tested false so far. So for now, at least, it is only active in Guinea and Liberia.
[1]: One clarification is that two people from Sierra Leone died from EVD while they were in Guinea, and their bodies were repatriated to Sierra Leone and buried there. Sierra Leone has since banned repatriation of bodies to mitigate the risk of it spreading through this vector.
Source: http://www.who.int/csr/don/archive/disease/ebola/en/