When Martin Salia’s Ebola test came back negative, his friends and colleagues threw their arms around him. They shook his hand. They patted him on the back. They removed their protective gear and cried.

But when his symptoms remained nearly a week later, Salia took another test, on Nov. 10. This one came back positive, sending the Sierra Leonean doctor with ties to Maryland on a desperate, belated quest for treatment and forcing the colleagues who had embraced him into quarantine.

“We were celebrating. If the test says you are Ebola-free, we assume you are Ebola-free,” said Komba Songu M’Briwa, who cared for Salia at the Hastings Ebola Treatment Center in Freetown. “Then everything fell apart.”

Salia died early Monday at the Nebraska Medical Center in Omaha, his family left to wonder what would have happened if he had received earlier treatment.

His widow, Isatu, lives in New Carrollton, and they have two children, 12 and 20, also living in the United States. He had been a visitor to their Maryland home, but has devoted most of his time to his medical work in Freetown.

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

In a sign that the Ebola epidemic still poses a danger, even though it may have eased in parts of Liberia, the Centers for Disease Control and Prevention announced Sunday that airport screening will begin for travelers arriving in the United States from Mali, which lies inland from Sierra Leone and Liberia and has begun to report cases of the disease.

For Sierra Leone’s medical establishment, already rocked by Ebola, another doctor’s diagnosis was devastating national news. Since the outbreak started, 320 Sierra Leonean health workers have died of the disease. New billboards in Freetown show the faces of doctors who have died, with the words “Some of our national heroes killed by Ebola.”

The hospital where Salia worked in Freetown has been shuttered, and three of his colleagues are being isolated in the surgery ward where he once treated patients.

The doctors who tended to him in Freetown appeared to be unaware that an early Ebola test — taken within the first three days of the illness — is often inconclusive. In a country where information about the disease continues to move slowly, it was another potentially tragic mistake.

In many cases, a negative test at that stage means nothing because “there aren’t enough copies of the virus in the blood for the test to pick up,” said Ermias Belay, the head of the CDC’s Ebola response team in Sierra Leone

But M’Briwa and others treated the test as definitive, even though Salia remained feverish and weak. The first results were delivered by a team of Chinese lab technicians who had opened a nearby hospital. (The technicians declined Sunday to speak about Salia’s case.)

Nancy Jongowai Neeconthe, a nurse who has worked with Salia for two years, saw that he was crying after the negative test result came back. Caught up in the emotional moment, she hugged him outside the Ebola ward, a converted police training base.

“Thank God,” she remembers saying.

But after he was released from Hastings, Salia’s symptoms worsened. He had a high fever and diarrhea. He vomited uncontrollably. He prescribed himself malaria medication, but it made no difference.

“I’m really feeling my body,” he told Neeconthe.

He called his colleague Alhali Osman Smith, who worked with him at Freetown’s Kissy United Methodist Hospital.

“He told me he thought he still might have Ebola,” Smith said, “in spite of what the test said.”

It took five more days for Salia to take a second Ebola test, this one administered by South Africans at Lakka Hospital in Freetown. It came back positive.

Although the United Methodist hospital where Salia and Smith work doesn’t treat Ebola, both doctors knew that their patients could be infectious. A woman giving birth, a man complaining of abdominal pain — any of them could be carrying the disease. Salia wore gloves but never the full protective gear used in the country’s Ebola wards. His colleagues say he couldn’t pinpoint how he had contracted the disease.

Salia had worked at the Methodist hospital for nearly three years. He also worked at Connaught Hospital, Sierra Leone’s largest government hospital, and lectured at the country’s only medical school. He seemed to be working all the time.

“His hobby was surgery,” said John K. Yambasu, bishop of the United Methodist Church in Sierra Leone and chairman of the Religious Leaders Task Force on Ebola.

After the second test, M’Briwa remembers that a team of American doctors came by Hastings to inquire about Salia and lay the groundwork for his evacuation.

The treatment center was overflowing. The disease had spread rapidly throughout Freetown and western Sierra Leone. The 120 beds at Hastings were no longer enough.

Still, the doctors tried to give Salia special treatment. They checked on him every hour. They let him spend time with patients who were soon to be released, rather than those in the ward, who writhed in their own filth.

One day, M’Briwa remembers, a 2-year-old boy who survived the disease approached Salia.

“I am fine, and you’re going to be fine, too,” the boy said.

On Saturday, Smith stood next to Salia’s ambulance near the Freetown airport’s tarmac. He held Salia’s passport for him, eventually handing it to a U.S. official, afraid that it would otherwise be contaminated by the disease.