The most impacted countries before 2014 were DRC, Gabon, Sudan and Uganda (natural reservoirs of the virus hosts)
The virus subtype linked to the most outbreaks and cases/deaths in the past is the Zaire virus. This can be tied to the recent tragic outbreak in West Africa also due to a Zaire virus subtype.
The severity of the last outbreak in a different area of Africa brings a few questions to mind. Is the reservoir of virus hosts moving/expanding? Is the severity due to an increased virulence of the Zaire subtype or to a delayed emergency response.