US President Barack Obama told West Africans on Tuesday that Ebola could be beaten but cautioned that it would not be easy to stem the spread of the deadly disease.

Obama appeared in a YouTube video to underline that it was vital to take basic precautions when dealing with those afflicted and in burying the dead to thwart infections.

"Stopping this disease won't be easy. But we know how to do it," said Obama, who feels a special kinship with Africa owing to his ancestral ties to the continent.

"You are not alone, together we can treat those who are sick with respect and dignity.

"We can save lives and our countries can work together to improve public health so this kind of outbreak doesn't happen again," said Obama in the video, which appears on the White House website and was aimed especially at Liberia, Sierra Leone, Nigeria and Guinea.

The president noted that Ebola could not be contracted through the air or from sitting next to someone on a bus, but was spread through the exchange of bodily fluids or sometimes through direct contact with the bodies of those who had died of the disease.

The head of the US Centers for Disease Control and Prevention, Tom Frieden, said that despite tremendous efforts from the US government, and affected West African nations, the number of Ebola infections was continuing to grow.

The Ebola outbreak has killed 1,552 people and infected 3,062, according to the latest figures released by the World Health Organization.

"I'm afraid that over the next few weeks, those numbers are likely to increase further and significantly," Frieden said.

"We need action now to scale up the response. We know how to stop Ebola. The challenge is to scale it up to the massive levels needed to stop this outbreak. This is really the first epidemic of Ebola the world has ever known."

The US warnings echoed those of international medical agency Medecins Sans Frontieres, which said the world was "losing the battle" to contain Ebola and called for a global biological disaster response to get aid and personnel to West Africa.

"Six months into the worst Ebola epidemic in history, the world is losing the battle to contain it. Leaders are failing to come to grips with this transnational threat," MSF international president Joanne Liu told a UN briefing in New York.