DALLAS - The United States is establishing a rapid-response team to help hospitals "within hours" whenever there is a case of Ebola, the top doctor leading the fight against the deadly virus said on Tuesday.

Prospects for a quick end to the contagion fell as the World Health Organization (WHO) predicted that three impoverished countries in West Africa - Liberia, Sierra Leone and Guinea - could produce as many as 10,000 new cases per week by early December.

US Centers for Disease Control and Prevention (CDC) Director Dr. Thomas Frieden, acknowledging the lapses in treatment in Dallas for a Liberian man in late September, told reporters:

"I wish we had put a team like this on the ground the day the first patient was diagnosed ... but we will do that from today onward with any case in the US"

"We will be there, hands on, within hours, helping hospitals with the situation if there is another case," he said.

A nurse who contracted Ebola from the Liberian patient, Thomas Eric Duncan, in a Dallas hospital said on Tuesday she was doing well. The nurse, Nina Pham, 26, is "in good condition," Texas Health Presbyterian Hospital said in a statement.

US President Barack Obama, addressing defense chiefs from about 20 countries, said "the world as a whole is not doing enough" to combat the hemorrhagic fever and must stop it at its source.

Obama will hold a video conference on Wednesday with British, French, German and Italian leaders to discuss Ebola and other international issues, the White House said.

Health authorities say the outbreak in West Africa is the worst on record with at least 4,447 dead. An unrelated outbreak has killed more than 40 people in Democratic Republic of the Congo.

Ebola, which can cause fever, bleeding, vomiting and diarrhea, spreads through contact with bodily fluids such as blood or saliva. The Dallas nurse, Pham, became the first person infected by Ebola in the United States while caring for Duncan for much of his 11 days in the hospital. He died on Oct 8.

Pham received a transfusion on Monday containing antibodies to fight the virus, according to a Roman Catholic priest in her congregation. Duncan did not receive one because he did not match the donor's blood type. Christian relief group Samaritan's Purse has said that Dr. Kent Brantly, a physician who survived an Ebola infection, donated plasma to Pham.

"I'm doing well and want to thank everyone for their kind wishes and prayers," Pham said in a statement released by the hospital. "I am blessed by the support of family and friends."

The CDC's Frieden said at a news conference that 48 people who had potential contact with Duncan "have passed through the highest risk period" for developing Ebola symptoms. He said 76 people who may have come into contact with Duncan after he was hospitalized on Sept 28 now were being monitored. That group includes Pham and other health workers and hospital staff.