Dr Rick Sacra is being flown to Nebraska for treatment and is now the third missionary working for U.S. charity SIM to be taken back to America for help.
He's served as a Christian media in West Africa since 1995.
Last month Dr. Kent Brantly and Nancy Writebol who also worked with SIM were discharged from a hospital in the States after being cured.
They're now with their families and are taking some time to rest and recover their strength.
The doctor, 51, is the latest missionary to become ill with the virus that's killed almost 2,000 people in West Africa.
His wife, Debbie Sacra, said: "I am overwhelmed and abundantly blessed by all the kind words that people have said about Rick since the news of his sickness was released.
"When he left at the beginning of August, we understood there was a risk he could become sick with this deadly virus but I knew that he needed to go and be with the Liberian people who needed a hospital to be open."
She added: "He is not someone who can stand back when there is a need that he can take care of. His word to everyone who is watching these broadcasts is that the need in West Africa is desperate and there are resources that can be deployed to make sure that all healthcare workers have enough gloves and gowns and boots and thermometers to protect themselves from possible Ebola exposures and continue caring for those who need other medical care.
"Please find a practical way to meet the needs of Liberia and its neighbours in this time of fear and suffering. As Rick wrote to his medical colleagues, this epidemic is a wildfire about to rage out of control."