Dr Kent Brantly (right) of Samaritan's Purse relief organisation is shown in this undated handout photograph. Picture: Samaritan's Purse, via Reuters

Boone, North Carolina -

An American doctor infected with the deadly Ebola virus in West Africa received intensive treatment on Sunday and was in stable condition, talking to his medical team and working on his computer, a spokeswoman for an aid group said.

Dr Kent Brantly, 33, was being treated at a hospital in Monrovia, Liberia.

“We are hopeful, but he is certainly not out of the woods yet,” said Melissa Strickland, a spokeswoman for the US-based group Samaritan's Purse, where Brantly is the medical director. Early treatment improves a patient's chances of survival, and Strickland said Brantly recognised his own symptoms and began receiving care immediately.

The highly contagious Ebola virus is one of the most deadly diseases in the world. The World Health Organisation says this outbreak is the largest ever recorded, killing more than 670 people in Liberia, Guinea and Sierra Leone since it began earlier this year.

Health workers are at serious risk of contracting the disease, which spreads through contact with bodily fluids.

Photographs of Brantly working in Liberia show him in white coveralls made of a synthetic material that he wore for hours a day while treating Ebola patients.

Brantly was quoted in a posting on the organisation's website earlier this year about efforts to maintain an isolation ward for patients.

“The hospital is taking great effort to be prepared,” Brantly said. “In past Ebola outbreaks, many of the casualties have been healthcare workers who contracted the disease through their work caring for infected individuals.”

The WHO says the disease is not contagious until a person begins to show symptoms. Brantly's wife and children had been with him in Liberia but flew home to the US about a week ago, before the doctor started showing any signs of illness, Strickland said.

“They have absolutely shown no symptoms,” she said.

A woman who identified herself as Brantly's mother answered a US phone listing for him, but said family members were declining comment at this time.

A government official said on Sunday that one of Liberia's most high-profile doctors has died of Ebola, highlighting the risks facing health workers trying to combat the deadly disease.

Dr Samuel Brisbane was the first Liberian doctor to die in the outbreak. A Ugandan doctor working in Liberia died earlier this month. - Sapa-AP