US President Barack Obama has told west Africans that Ebola could be beaten, but cautioned that it would not be easy to stem the spread of the deadly disease.
Mr 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," Mr Obama, who feels a special kinship with Africa owing to his ancestral ties to the continent, said.
"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," Mr Obama said in the video, which appears on the White House website and was aimed especially at Liberia, Sierra Leone, Nigeria and Guinea.
The US 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," Mr 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.
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.
UN warns over risk to harvest
The Ebola epidemic has put harvests at risk and sent food prices soaring in West Africa, the UN Food and Agriculture Organisation said.
It warned that the problem would intensify in coming months.
The FAO issued a special alert for Liberia, Sierra Leone and Guinea, the three countries most affected by the outbreak.
More than 1,550 people have died since the virus was detected in the remote jungles of southeastern Guinea in March.
Restrictions on people's movements and the establishment of quarantine zones to contain the spread of the hemorrhagic fever has led to panic buying, food shortages and price hikes.
"Even prior to the Ebola outbreak, households in some of the most affected areas were spending up to 80% of their incomes on food," said Vincent Martin, head of an FAO unit in Dakar which is coordinating the agency's response.
"Now these latest price spikes are effectively putting food completely out of their reach," Mr Martin said in a statement.
He said the food crisis could hinder containment of the disease, which is typically spread via the bodily fluids of the sick.
Rice and maize production will be scaled back during the fast-approaching main harvest season as migration and movement restrictions cause labour shortages on farms, FAO said.
The UN World Food Programme and FAO have approved an emergency programme to deliver 65,000 tonnes of food to 1.3 million people affected by Ebola over a three-month period.
