The British nurse who survived Ebola will begin his second spell treating people infected by the deadly virus after returning to the country where he caught the infection.
William Pooley said he was "delighted" to go back to Sierra Leone in West Africa as he attempts to prevent "as many unnecessary deaths as possible".
The 29-year-old arrived in the capital Freetown yesterday and he will now resume work in an Ebola isolation unit run by UK medical staff, King's Health Partners said.
Mr Pooley became the first confirmed Briton to contract Ebola and was flown back to the UK in August, where he was treated at the Royal Free Hospital in London.
It comes after a Spanish nursing assistant who became the first person to contract Ebola outside Africa was found to be clear of all traces of the virus.
A blood test has revealed that Teresa Romero's immune system has eliminated the infection from her body, according to a statement released by Prime Minister Mariano Rajoy's office.
Mr Pooley said: "I am delighted to be returning to Sierra Leone to join the King's Health Partners team. I would like to once again thank the team at the Royal Free Hospital and the RAF who provided me with such excellent treatment and support.
"But the real emergency is in West Africa, and the teams out there need all the support we can give them.
"I am now looking forward to getting back out there and doing all I can to prevent as many unnecessary deaths as possible."
Mr Pooley will be working in the isolation unit at Connaught Hospital where he will train local staff and help to set up new isolation units, after previously treating patients in a government hospital in Kenema.
He will join the King's Health Partners team, a partnership between King's College London and three NHS trusts - Guy's and St Thomas', King's College Hospital and South London and Maudsley.
Dr Oliver Johnson, programme director for the King's Sierra Leone Partnership, said: "It is fantastic that Will has chosen to join our small team here at Connaught Hospital.
"The situation here in Freetown is getting worse by the day and so Will's experience and commitment will be vital as we do everything we can to stem the flow of cases.
"The best way of stopping Ebola spreading even further is to fight it at its source and I look forward to working with Will to do just that."
Mr Pooley was treated with the experimental drug ZMapp and left hospital on September 3 after making a full recovery.
Last week he said he was preparing to return to West Africa to help deal with the Ebola epidemic because it is "something I need to do".
Speaking in Whitehall in central London, the nurse said he knew his family and friends would be worried but they should be reassured by his potential immunity to the virus.
"There is still a lot of work to do out there and I am in the same or better position than when I chose to go out before," Mr Pooley said.
"I know my mum and dad are worried but they support me because they know this is something I have to do.
"My potential immunity is very reassuring for them, or at least it should be, and I will be returning in a more organised fashion than when I was out there originally."
Last month Mr Pooley, from Eyke in Suffolk, reportedly flew to the US to undergo a blood transfusion to help an American being treated for the virus.
More than 4,500 people have died from Ebola, mainly in Guinea, Liberia and Sierra Leone.
Britain's latest Ebola aid flight carrying vital medical supplies landed in Freetown on Saturday, International Development Secretary Justine Greening said.
It was the UK's sixth aid flight and carried almost £900,000 worth of medical equipment needed for the 92 bed treatment facility in Kerry Town, including blood banks, centrifuges and protective equipment such as goggles and gloves.
The UK, which has committed £125 million to tackling Ebola, has put pressure on other wealthy countries to do more to combat the spread of the virus.
The Prime Minister has written to European Union leaders calling for them to double their contribution to one billion euro (£800 million) this week.
Foreign Secretary Philip Hammond was meeting fellow EU foreign ministers in Luxembourg to draw up a co-ordinated European response to the Ebola outbreak.
Backing the PM's call for more funding from other EU states, Mr Hammond told the BBC: "We do need this billion-euro fund. There is a major health crisis here. We've got a very short window to get on top of it and prevent the uncontrollable spread of this disease.
"This is a very worthwhile investment and that money would be spent on providing additional beds and isolation facilities in-country, because the only way we are going to stop the spread of the disease is to make sure that people are isolated and treated early."