The death toll has hit 337 since February, the U.N. World Health Organisation said last week, making it the deadliest outbreak since Ebola first emerged in 1976.
The disease has not previously occurred in the region and local people remain frightened of it and view health facilities with suspicion. This makes it harder to bring it under control, MSF said in a statement.
At the same time, MSF said, a lack of understanding has meant people continue to prepare corpses and attend funerals of Ebola victims, leaving them vulnerable to the disease, transmitted by touching victims or through bodily fluids.
Civil society groups, governments and religious authorities have also failed to acknowledge the scale of the epidemic and as a result few prominent figures are promoting the fight against the disease, the statement said.
"The epidemic is out of control," said Bart Janssens, MSF director of operations. "With the appearance of new sites in Guinea, Sierra Leone and Liberia, there is a real risk of it spreading to other areas."
MSF has treated some 470 patients, 215 of them confirmed cases, in specialised centres in the region but the organisation said it had reached the limit of its capacity.
Patients have been identified in more than 60 locations across the three countries making it harder to curb the outbreak.
Ebola has a fatality rate of up to 90 percent and there is no vaccine and no known cure. The virus initially causes raging fever, headaches, muscle pain, conjunctivitis and weakness, before moving into more severe phases with vomiting, diarrhoea and haemorrhages.
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