A surgeon infected with Ebola while treating patients in Sierra Leone has died in Nebraska, Nebraska Medical Center announced Monday.

Dr. Martin Salia arrived in Omaha on Saturday morning for treatment at the Nebraska Medicine biocontainment unit.

“It is with an extremely heavy heart that we share this news,” Dr. Phil Smith, medical director of the Biocontainment Unit at Nebraska Medical Center said in a statement posted on the hospital’s Facebook page, . “Dr. Salia was extremely critical when he arrived here, and unfortunately, despite our best efforts, we weren’t able to save him.”

Nebraska Medicine is preparing to release more details of Salia’s death on Monday morning at 11 a.m.

Salia, who was diagnosed with Ebola a week ago, landed at Eppley Airfield in Omaha on Saturday for treatment at the Nebraska Medicine biocontainment unit.

The medical crew transporting Salia, 44, determined he was stable enough to fly, but that information from the team caring for him in Sierra Leone indicated he was critically ill and “possibly sicker than the first patients successfully treated in the United States.”

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

At first, Salia thought he had malaria or typhoid. His wife says he had two negative tests for Ebola before the third came back positive.

Salia, called “one of the best trained surgeons in his country” by colleagues, had been working as a general surgeon at Kissy United Methodist Hospital in Freetown, Sierra Leone.