OMAHA, Neb. -- A surgeon who contracted Ebola while working in his native Sierra Leone has died while being treated in a biocontainment unit at a Nebraska hospital, the facility said Monday.

Nebraska Medical Center said in a news release that Dr. Martin Salia died as a result of the disease.

"Dr. Salia was extremely critical when he arrived here, and unfortunately, despite out best efforts, we weren't able to save him," said Dr. Phil Smith, medical director of the biocontainment unit.

Salia arrived Saturday to be treated at the Omaha hospital, where two other Ebola patients have been successfully treated.

Ebola has killed more than 5,000 people in West Africa, mostly in Liberia, Guinea and Sierra Leona.

The 44-year-old Salia had been working as a general surgeon at Kissy United Methodist Hospital in the Sierra Leone capital of Freetown. It's not clear whether he was involved in the care of Ebola patients. Kissy is not an Ebola treatment unit, but Salia worked in at least three other facilities, United Methodist News said, citing health ministry sources.

Salia, a Sierra Leone citizen who lives in Maryland, first showed Ebola symptoms on Nov. 6 but tested negative for the virus. He eventually tested positive on Nov. 10.