Another American Ebola patient is headed to Emory University Hospital in Atlanta for treatment, according to a statement from the hospital. The patient is expected to arrive Tuesday morning.

The patient, who has not been named, will be the fourth known American to have contracted the virus in an outbreak that has killed 1,848 people and sickened 1,849 others, according to the latest data from the World Health Organization. The patient is traveling via air ambulance from West Africa to receive treatment where two other American Ebola survivors -- Dr. Kent Brantly and missionary Nancy Writebol – received supportive care and were later declared virus-free. Writebol was discharged Aug. 19 and Brantly went home two days later.

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Brantly and Writebol both contracted the virus while tending to patients in Monrovia, Liberia. It is not yet clear where in West Africa the latest American patient contracted the virus.

Last week, Dr. Rick Sacra became the third American -- and the second American doctor -- to contract Ebola. He, too, was treating patients in Monrovia, Liberia, but he was treating them in the ELWA hospital maternity ward, not the Ebola facility. Sacra is undergoing care at Nebraska Medical Center in Omaha.