Aid organisation Doctors Without Borders says an Ebola outbreak suspected of killing at least 78 people in Guinea is an "unprecedented epidemic" that has spread across the west African nation.

"We are facing an epidemic of a magnitude never before seen in terms of the distribution of cases in the country: Gueckedou, Macenta, Kissidougou, Nzerekore, and now Conakry," Mariano Lugli, the organisation's co-ordinator in the Guinean capital, said in a statement on Monday.

MSF said by the end of the week it would have around 60 international field workers with experience in working on haemorrhagic fever divided between Conakry and the southeast of the country.

Its team includes doctors, nurses, epidemiologists, water and sanitation experts as well as anthropologists.

"MSF has intervened in almost all reported Ebola outbreaks in recent years but they were much more geographically contained and involved more remote locations," Lugli said.

"This geographical spread is worrisome because it will greatly complicate the tasks of the organisations working to control the epidemic."