Dr Kent Brantly makes chlorine solution for disinfection at the case management centre on the campus of ELWA Hospital in Monrovia, Liberia, in this undated handout photo.

An American doctor stricken with the deadly Ebola virus while in Liberia and brought to the United States for treatment in a special isolation ward is improving, the top US health official said yesterday.

Dr Kent Brantly, a 33-year-old father of two young children, was able to walk, with help, from an ambulance after he was flown on Saturday to Atlanta, where he was being treated by infectious disease specialists at Emory University Hospital.

“It’s encouraging that he seems to be improving – that’s really important – and we’re hoping he’ll continue to improve,” Dr Tom Frieden, director of the US Centres for Disease Control in Atlanta, said on CBS’s Face the Nation.

Frieden told the programme it was too soon to predict whether Brantly would survive, but said it was unlikely that Brantly’s wife and children, who left Liberia shortly before he began exhibiting symptoms, had contracted the disease.

People who are exposed to Ebola but are not sick cannot infect others, Frieden said. Brantly, who works for the North Carolina-based Christian organisation Samaritan’s Purse, had been in Liberia responding to the worst Ebola outbreak on record when he contracted the disease. Since February, more than 700 people in West Africa have died from the infection.

Ebola is a hemorrhagic virus with a death rate of up to 90 per cent of those who become infected. The fatality rate in the current epidemic is about 60 per cent.

A second US aid worker who contracted Ebola while working in the same facility as Brantly, missionary Nancy Writebol, will be brought to the US on a later flight as the medical aircraft is equipped to carry only one patient at a time.

Officials have said that Writebol, a 59-year-old mother of two, was expected to arrive this week in Atlanta.

Writebol’s husband David, who had been living and working in Liberia with his wife, was expected to travel home separately within the next few days, their missionary organisation, SIM USA, said in a statement.

Despite concern over bringing Ebola patients to the country, the CDC’s Frieden said the US may see only a few isolated cases in people who have been traveling.