Time magazine on Wednesday named as its "Person of the Year 2014" the medics treating the Ebola epidemic that has killed more than 6,300 people, paying tribute to their courage and mercy.

The hemorrhagic fever mushroomed from an outbreak into an epidemic in Liberia, Guinea and Sierra Leone, and there have been scattered cases in Nigeria, Mali, Spain, Germany and the United States.

"The rest of the world can sleep at night because a group of men and women are willing to stand and fight," wrote Time editor Nancy Gibbs, announcing the prestigious annual title.

"For tireless acts of courage and mercy, for buying the world time to boost its defenses, for risking, for persisting, for sacrificing and saving, the Ebola fighters are Time's 2014 Person of the Year."

The worst-ever Ebola outbreak has left more than 6,300 people dead worldwide, nearly all in Sierra Leone, Guinea and Liberia.

Time said the virus struck doctors and nurses in unprecedented numbers, "wiping out a public-health infrastructure that was weak in the first place."

Nina Pham, a Texas nurse who contracted Ebola while caring for the first patient diagnosed with the killer virus on US soil, said she was delighted to be part of the accolade.

"So honored to be a part of @Time Magazine's POY!" she tweeted.

Pham and another nurse at Texas Health Presbyterian Hospital in Dallas became infected with Ebola while caring for Thomas Eric Duncan, who died on October 8.

Both nurses survived.

Duncan was diagnosed with the disease after travelling from his homeland Liberia to the United States, where he was initially sent home from hospital.

On Tuesday, the United Nations' Ebola czar, David Nabarro, welcomed widespread progress in the fight against the deadly virus, but warned the outbreak was still surging in western Sierra Leone and northern Guinea.

He said more foreign health workers and specialists were needed in areas where the disease was still spreading quickly, as were more treatment units and beds.

Gibbs said governments were not equipped to respond to the crisis, the World Health Organization was in denial and snarled in red tape, and first responders were accused of crying wolf.

"This was a test of the world's ability to respond to potential pandemics, and it did not go well.

"It exposed corruption in African governments along with complacency in Western capitals and jealousy among competing bureaucrats," Gibbs wrote.

She paid tribute to the people in the field, those sent by charities such as Doctors Without Borders, as well as local doctors and nurses, ambulance drivers and burial teams.

"Ebola is a war, and a warning. The global health system is nowhere close to strong enough to keep us safe from infectious disease," wrote Gibbs.

"And 'us' means everyone, not just those in faraway places where this is one threat among many that claim lives every day."

The runners-up chosen by Time were protesters who took to the streets in the St Louis suburb of Ferguson to condemn the killing of unarmed black teenager Michael Brown by a white police officer.

Also shortlisted were Russian President Vladimir Putin, Massoud Barzani, president of Iraq's Kurdistan region, and China's richest man Jack Ma, founder of e-commerce giant Alibaba.