An American cameraman helping to cover the Ebola outbreak in Liberia has tested positive for the virus and will be flown back to the US for treatment.

NBC News identified the freelance cameraman on its website as 33-year-old Ashoka Mukpo.

Network president Deborah Turness said the rest of the crew, including medical correspondent Nancy Snyderman, will be flown back to the US and placed in quarantine for 21 days "in an abundance of caution".

Mr Mukpo has been working in Liberia for three years and has been covering the Ebola epidemic. He began shooting for NBC News on Tuesday.

He began feeling tired and achy on Wednesday and discovered he had a slight fever. He went to a treatment centre yesterday to be tested, and is being kept there, said Ms Snyderman on The Rachel Maddow Show on MSNBC.

Ms Snyderman said she believes his exposure to the virus happened some time before he started working with the NBC crew, since it is usually eight to 10 days before the first symptoms are seen.

"The good news is this young man, our colleague, was admitted to the clinic very, very early," she said.

"He's in good spirits. He's ready to get home - of course, appropriately concerned. But he will be airlifted out soon."

She said she and the other three NBC employees had shown no symptoms or warning signs of Ebola infection.

"We observe the custom now, which is to not shake hands, to not embrace people, to wash our hands with diluted bleach water before we enter the hotel," she said. "We dip our feet in bleach solution."

She said she and the rest of her crew present little chance of giving it to anyone, unless they get sick.

"We will be taking our temperatures twice a day, checking in with each other, and if any one of us suddenly spikes a fever or gets symptoms, we will report ourselves to the authorities. We are taking it seriously."