"States with the required capacity have a political and humanitarian responsibility to come forward and offer a desperately needed, concrete response to the disaster unfolding in front of the world's eyes ... rather than limit their response to the potential arrival of an infected patient in their countries," said Dr. Joanne Liu, chief of the group based in Geneva, Switzerland.
Her comments Tuesday came after U.S. Centers for Disease Control and Prevention Director Dr. Tom Frieden said in an interview that measures, such as flight restrictions to the target area of West Africa, are having the effect of "making it really hard to get help in and to respond effectively to the outbreak. What we're seeing is a ... hugely fast increase in cases that's harder and harder to manage. The more we can get in there and tamp that down, the fewer cases we'll have in the weeks and months to come."
Liberian President Ellen Johnson Sirleaf, in another interview, called on nations to "please work with us."
"Give us hope by joining us in this fight. Don't instill fear. We need that hope, we need that assistance, we need for Liberians to know that this war can be won," she said.
Over 3,000 people have been infected by the Ebola virus since the first case was documented in December 2013, the World Health Organization said.In Liberia, Guinea, Sierra Leone and Nigeria at least 1,552 people have died of the disease.