A surgeon who was infected with Ebola while treating the sick in his native Sierra Leone says his work there was "God's calling". 

Dr Martin Salia was being flown back to the US for specialist treatment and was due to arrive at the Nebraska Medical Center, Omaha, on Saturday. 

He is a permanent citizen of the US but felt a strong calling to go to Freetown to help amid the Ebola outbreak there. 

He told NBC he felt God wanted him to go there and that he was ready to put his trust in Him regardless of what happened.

"There was just something inside of me, that the people in this part of Freetown needed help," he said.

"I see it as God's own desired framework for me.  I took this job not because I want to but because I firmly believe it was a calling and God wanted me to.  

"That's why I strongly believe that the God who has brought me here will fix whatever comes my way.  I'm confident I just need to lean on him, trust him whatever comes in because he sent me here." 

The Nebraska Medical Center has successfully treated a doctor and a NBC cameraman for Ebola but Dr Phil Smith, medical director of the biocontainment unit, said in a statement that Dr Salia is "possibly sicker than the first patients successfully treated in the United States".