A doctor who was being treated for Ebola at the Nebraska Medical Center has died, the hospital said Monday.

"We are extremely sorry to announce that the third patient we've cared for with the Ebola virus, Dr. Martin Salia, has passed away as a result of the advanced symptoms of the disease," the hospital in a statement said.

Salia is a native of Sierra Leone. He was infected with Ebola while working in his home country.

The 44-year-old had been working as a general surgeon at Kissy United Methodist Hospital in the Sierra Leone capital of Freetown, according to health ministry sources. It's not clear whether he was involved in the care of Ebola patients because Kissy is not an Ebola treatment unit.

He was flown to Nebraska for treatment on Saturday and by late Sunday was in critical condition. Reports said that he was suffering from kidney and respiratory failure when he arrived on Nov. 15.

"We used every possible treatment available to give Dr. Salia every possible opportunity for survival," said Dr. Phil Smith, medical director of the biocontainment unit.

"As we have learned, early treatment with these patients is essential. In Dr. Salia's case, his disease was already extremely advanced by the time he came here for treatment."

Salia was the 10th person with Ebola to be treated in the United States, and the second to have died from the virus. He was the sixth doctor to be infected with the deadly disease in Sierra Leone; all previous five have died.

Back in October, a Liberian native, Thomas Duncan died at a hospital in Dallas Texas from Ebola.

Two other Ebola patients, a doctor and a journalist, were treated at the Nebraska hospital and survived.

The World Health Organization said Friday that 5,177 people are known to have died of Ebola across eight countries, out of a total 14,413 cases of infection, since December 2013.