The cumulative average considering all ebola cases and deaths from 1976 to the present is actually closer to 60-to-65% and the current outbreak has a CFR of about 54% - though it's subject to change as the outbreak goes on."
This figure of 54%, however, is an average taken from several countries. The fatality rate varies from one country to another - in Guinea it's about 73%, whereas in Liberia its 55%, and in Sierra Leone it's 41%.
Why the variation?
The main factors, according to Majumder, are the level of preparedness and the availability and quality of medical care.