"I firmly believe that it was a calling and that God wanted me to," Martin Salia said in an April 2014 interview about why he worked to treat Ebola patients at Kissy Hospital in Freetown, Sierra Leone. Salia died of the disease on Monday. (United Methodist Communications via YouTube)

By the time Martin Salia arrived on a chartered medical jet at the Nebraska Medical Center over the weekend, his kidneys had failed, he didn’t respond to someone calling his name, and he was barely breathing.

Doctors immediately put the 44-year-old surgeon, who had been infected by Ebola while working at hospitals in his native Sierra Leone, on emergency kidney dialysis and a ventilator. They gave him an experimental treatment called ZMapp and plasma from an Ebola survivor — treatments that have been used with other patients who have recovered from the disease at U.S. hospitals.

In the end, Salia was too sick, his body riddled with the deadly virus. He died early Monday, more than 5,000 miles from the hopeful colleagues who 10 days ago rejoiced with him when an initial test for Ebola came back negative.

“We are reminded that even though this was the best possible place for a patient with the virus to be, that in its very advanced stages, even the most modern techniques we have at our disposal aren’t enough to help these patients once they reach a certain threshold,” said Jeff Gold, chancellor of the University of Nebraska Medical Center, the hospital’s academic partner. “We are very, very sorry the outcome wasn’t the one we all wished for.”

In Freetown, one of Salia’s colleagues, Alhali Osman Smith, got a call from Salia’s wife, who was in Nebraska.

“He’s gone,” she said.

Smith broke down immediately. Salia had been his mentor in the years they worked together in Freetown, Sierra Leone’s capital. Like Salia’s other colleagues and former students, Smith remembered him as one of the country’s hardest-working doctors, a man who always craved more knowledge about the profession he loved.

“He taught me that, as a doctor, you never stop learning,” Smith said Monday evening in Freetown, where news of Salia’s death was broadcast on the radio.

Salia’s death highlights what experts say is a critical need in the ongoing fight against the worst Ebola outbreak in history: the ability to quickly and accurately diagnose the disease in order to halt its spread and give patients the best chance for survival.

Salia, whose wife, a U.S. citizen, and two children live in Maryland, had tested negative for the disease shortly after developing symptoms, and he celebrated with colleagues in Freetown. That joy turned to anguish when a confirmatory test came back positive three days later, on Nov. 10. By the time he arrived in Nebraska, it had been 13 days since he started showing symptoms, hospital officials said.

“As we have learned, early treatment with these patients is essential,” said Phil Smith, medical director of Nebraska’s biocontainment unit, where Salia was treated. The hospital’s two surviving Ebola patients arrived on day six and day eight of their illnesses.

The Ebola virus typically can be detected in blood only after the onset of symptoms, usually a fever. It may even take several days after symptoms appear for the disease to show up in a commonly used blood test that looks for the genetic core of the virus. If an initial test is performed less than three days after symptoms appear and is negative, experts recommend a later test to rule out the virus, according to officials from the Centers for Disease Control and Prevention.

During a news conference Monday, University of Nebraska Medical Center Chancellor Jeff Gold said the death of surgeon Martin Salia, who was treated at that hospital for Ebola, serves as a reminder of how deadly the virus can be in its advanced stages. (University of Nebraska Medical Center)

“In the early stages of the illness, the virus may not be present in the blood in sufficient quantity to detect,” said Amesh Adalja, a senior associate at the University of Pittsburgh Medical Center’s Center for Health Security. There is a “window period,” he said, in which a person has been infected but current tests do not yet detect the virus.

There has been a big push in recent months to develop rapid tests that can more quickly provide a diagnosis. But even those tests wouldn’t necessarily be able to help doctors diagnose Ebola soon after a person is infected but before symptoms begin.

“Everybody realizes that is an important goal,” said Thomas Geisbert, a professor at the University of Texas Medical Branch at Galveston and a veteran Ebola researcher. “The earlier you treat, your success rate goes up dramatically.”

Hospital officials in Nebraska said they were contacted Thursday by the State Department, which had received a request from Salia’s wife. Although the U.S. military recently opened a field hospital in Liberia designed to treat infected health-care workers, the decision was made to bring Salia to the United States so he could be closer to his family, according to an Obama administration official.

The hospital contacted the makers of ZMapp on Friday and discovered that the company still had some of the scarce drug, said Chris Kratochvil, associate vice chancellor for clinical research at the University of Nebraska Medical Center. The company shipped the experimental medicine overnight.

In a statement, Salia’s wife, Isatu Salia, who lives in New Carrollton with their two sons, thanked the hospital’s staff for trying to save her husband’s life. “We’re very grateful for the efforts of the team led by Dr. Smith,” she said. “In the short time we spent here, it was apparent how caring and compassionate everyone was.”

Local officials of the United Methodist Church, which sponsors the hospital where Salia worked in Freetown, described him as committed to helping the poorest and sickest inhabitants of his native country, long before the Ebola outbreak erupted.

“He chose to work with people who were marginalized and had no place else to go” for medical treatment, said the Rev. Maidstone Mulenga, assistant to Bishop Marcus Matthews of the United Methodist Baltimore-Washington Conference.

In an interview in April with United Methodist officials, Salia spoke of his job as a calling.

“Why did I decide to choose this job? I firmly believe God wanted me to do it. And I knew deep inside myself there was just something inside of me that the people in this part of Freetown needed help,” he said, a smile spreading across his face. “I’m confident that I just need to lean on Him, trust Him for whatever comes in. Because He sent me here, and that’s my passion.”

Kevin Sieff in Freetown, Emily Wax and Pam Constable contributed to this story.