The Ebola outbreak is the "most severe acute health emergency in modern times", the World Health Organisation has warned.
The agency's director-general Margaret Chan said the epidemic had proved "the world is ill-prepared to respond to any severe, sustained, and threatening public health emergency".
She added that new cases of Ebola are now "rising exponentially" in the three hardest-hit countries, Guinea, Liberia, and Sierra Leone.
In a statement to a regional health conference in the Philippine capital Manila, she said: "I have never seen a health event threaten the very survival of societies and governments in already very poor countries.
"I have never seen an infectious disease contribute so strongly to potential state failure."