A doctor said to be "extremely ill" after being infected with Ebola in Sierra Leone was being treated in the United States on Sunday, while the world's most powerful economies vowed to "extinguish" the deadly epidemic.
Martin Salia, a US resident who was infected with the deadly hemorrhagic fever while treating patients in his home country, was flown to Nebraska for treatment.
World leaders meeting at the G20 summit in the Australian city of Brisbane said they were prepared "to do what is necessary to ensure the international effort can extinguish the outbreak".
Ebola has killed more than 5,100 people, mostly in Guinea, Liberia and Sierra Leone, since the outbreak began earlier this year.
Mali was also scrambling to prevent a new outbreak of the disease that has killed three people in the desert nation, despite hopeful signs elsewhere in Africa.
Liberia has lifted its state of emergency and the Democratic Republic of Congo announced the end of its own outbreak of the disease.
In London, musicians including boy band One Direction and Led Zeppelin's Robert Plant recorded a new "Band Aid" single to help combat the virus.
In Brisbane, G20 members welcomed an International Monetary Fund initiative to release $300 million to combat Ebola and promised to share best practices on protecting health workers on the front line.
In the United States, attention was focused on the University of Nebraska Medical Center where Salia arrived in an "extremely critical condition" Saturday from Sierra Leone's capital Freetown where he had gone to treat Ebola patients.
"This is an hour-by-hour situation," said Phil Smith, medical director of the biocontainment unit at UNMC, one of a handful of medical facilities in the United States specially designated to treat Ebola patients.
"He is extremely ill," Smith said. "We will do everything humanly possible to help him fight this disease."
Salia is the third Ebola patient to be treated by the UNMC -- the previous two survived.
Of the nine Ebola patients treated in the United States before Salia's arrival, only one has died: Liberian Thomas Eric Duncan.
In sharp contrast, the disease has proved deadly in an estimated 70 percent of cases in west Africa.
- 'Mali situation worrying' -
The G20 pledge came as Togo, whose president is coordinating the west African fight, warned that the world "cannot relax efforts" despite some encouraging signals.
Senegal said Friday it was reopening its air and sea borders with Guinea, Liberia and Sierra Leone, although its land border with Guinea will remain closed.
The news came a day after Liberia lifted its state of emergency after announcing huge gains in fighting Ebola.
The DR Congo -- where a three-month outbreak of a different strain of the disease claimed at least 49 lives since August -- declared itself Ebola-free on Saturday.
But Mali is the latest source of concern, where there are fears an isolated outbreak could spark a major crisis after the deaths of three people infected by a Guinean imam who died of Ebola.
A fourth person, a doctor at the Bamako clinic where the cleric died, is in intensive care. More than 250 people have been placed under observation.
Former colonial power France added Mali to its list of destinations subject to Ebola flight checks.
"The situation in Mali is worrying," French development minister Annick Girardin said in the Guinean capital Conakry, adding she would meet Malian authorities "to see how we can scale things up."
There is no known cure for Ebola, one of the deadliest known pathogens, but trials for several possible treatments were announced this week in west Africa and Canada. The disease spreads through contact with bodily fluids.
The World Health Organization said Friday that 5,177 people are known to have died of Ebola across eight countries, out of a total 14,413 cases of infection, since December 2013.
- Makes humans 'untouchable' -
UN chief Ban Ki-moon urged "G20 countries to step up," warning that Ebola's disruptive effect on farming could potentially spark a food crisis for a million people.
"Transmission continues to outpace the response from the international community," Ban told reporters.
Artists also including U2 frontman Bono, Coldplay's Chris Martin and Sinead O'Connor recorded late into the night for a 30th anniversary version of the charity single "Do They Know It's Christmas?"
"It's not just about what's happening in west Africa, it could happen here tomorrow," said rocker-turned-activist Bob Geldof, one of the forces behind the original Band Aid.
Set to air on Sunday before its official release Monday, the single will be the fourth incarnation of the song, which became one of the biggest-selling singles ever after its release in 1984 to raise funds for Ethiopian famine relief.