Dr. David Schnabel, epidemic intelligence service officer with the Maryland Department of Health and Mental Hygiene, works with database training of Ministry of Health staff at the Bo District Surveillance Office in Sierra Leone in August. (Gbessay Saffa)

Rajiv Shah returned from the Ebola hot zone last week. The head of the U.S. Agency for International Development had spent several days traveling in Liberia, Sierra Leone and Guinea, where USAID announced $142 million in humanitarian projects and grants to combat Ebola in West Africa.

When he flew back to Washington, Shah joined a small army of American doctors, diplomats, aid workers, medical researchers, military personnel, journalists and others here who have been traveling back and forth from the epicenter of the Ebola epidemic for months.

On Thursday night, the risk of their work was on full display when a New York doctor who had treated Ebola patients in Guinea was diagnosed with the disease. Craig Spencer, 33, had volunteered to travel to West Africa for Doctors Without Borders, the international relief group that has been on the front lines of the crisis. He is being treated in an isolation unit at Bellevue Hospital.

His illness has prompted federal officials to consider the idea of quarantining medical workers after they return from West Africa, but no decision has been made.

Local health officials in Maryland, Virginia and the District say they are ready if there’s an Ebola case in the Washington region. The National Institutes of Health in Bethesda is one of four isolation facilities in the U.S. designated to treat Ebola patients. Nina Pham, the first nurse diagnosed with Ebola in this country, was released from NIH Friday after being declared virus free. But Pham was exposed to the virus at a hospital in Dallas, not in West Africa.

A CDC medical officer demonstrates the correct procedure for health-care workers to put on protective equipment. He is using the protocol recommended by Doctors Without Borders to prevent being infected with Ebola. (Jorge Ribas/The Washington Post)

Many of the Americans who volunteer to work in Guinea, Sierra Leone or Liberia stay as long as five weeks. Then they fly home, go back to work and resume their daily routines, while quietly monitoring their temperatures for 21 days and fielding sometimes fearful questions from colleagues, friends and neighbors about just how close they were to the virus.

On Wednesday, the Centers for Disease Control and Prevention announced new rules mandating “active monitoring” for everyone traveling from Guinea, Sierra Leone or Liberia, the three countries with nearly 10,000 reported Ebola cases and almost 5,000 deaths. Those travelers, including journalists, scientists and aid and health-care workers, will be required to provide home addresses, phone numbers and contacts for relatives and friends. State and local health departments will check on them daily for 21 days from the date they left West Africa.

Many Ebola commuters are already following those rules. Their first steps to avoid Ebola begin long before they landed in Africa. Before leaving Washington, they receive medical briefings, vaccinations and training for assignments in Ebola epicenters. They are advised on no-touch protocols to limit their exposure.

During his swing through West Africa, Shah met with the presidents of Liberia, Sierra Leone and Guinea and said his temperature was checked before he entered any government building.

“Before you walk into any building, there is a bucket of chlorinated water,” he said. “No one is shaking hands. You do an elbow bump.”

Shah said he followed all the protocols: “I washed my hands 25 times a day with chlorine wash. I did all the elbow bumps, no hand shaking.”

Because he did not have direct contact with Ebola patients or have a fever or any other symptoms associated with the disease, he was deemed a person of “no known exposure” under CDC guidelines when he returned to Washington. Within hours of landing, Shah went to the White House to meet with health and national security advisers about the U.S. response to the Ebola crisis.

“I took all appropriate precautions during my trip, and I have been actively monitoring my temperature since I have returned,” he said. “I have not had anyone on my staff express discomfort with working with me.”

CDC guidelines instruct that people deemed as having “no known exposure” and no symptoms do not need to be restricted in their movement. Anybody considered at “high risk of exposure,” such as those having direct contact with bodily fluids, blood, the skin of an Ebola patient or a dead body without protective equipment, would be required to travel by medical transport and undergo medical evaluations. If they are “asymptomatic,” they would be quarantined for 21 days after their last known exposure.

One of the most difficult challenges upon return is facing the stigma of having worked recently in West Africa. This month, Washington Post photojournalist Michel du Cille, who had covered the Ebola epidemic in Liberia, was uninvited to a journalism workshop at Syracuse University. School officials did not want him or his wife, Nikki Kahn, on campus, even though du Cille had been back from West Africa for three weeks and showed no symptoms of the disease.

Sarah Crowe, UNICEF chief of crisis communications, has encountered similar trepidation. She returned to New York this month after spending five weeks in Liberia. She mentioned the trip while riding a public bus.

“The driver asked whether I should really be on the bus,” said Crowe, who checks her temperature morning and evening. “I think it’s because of the peculiar uniqueness of Ebola that people react this way — the fear of the unknown. In a sense, my mission has been to demystify that fear.”

David Schnabel, a former Army doctor who lives in Baltimore, said he hasn’t talked much with people he doesn’t know about his five-week trip to Sierra Leone. Schnabel, who was working for the CDC in the hard-hit Bo District, returned on Sept. 29.

“I can tell you I did not broadcast where I had been before or after I returned to strangers,” said Schnabel, who trained Sierra Leoneans on Ebola safety protocols rather than caring for patients. “I understood the emotional response to Ebola. To protect myself from any stigma, I consciously was careful who I told.”

While he was in Sierra Leone, he was vigilant about avoiding direct contact with Ebola patients, avoiding the isolation wards at treatment centers.

He knew there was a risk of walking in the halls, “but I had to go in there because I knew that is where the work was.” But he said he never sat down. “I would never touch a wall. I would never lean against a wall. I would never set my notebook down. I would try to spray my shoes with chlorine wash.”

Schnabel’s partner, Sufia Dadabhai, 34, an epidemiologist at Johns Hopkins School of Public Health, said most of their friends work in public health, and no one expressed any overt fear of being near Schnabel when he returned.

“The people we wanted to go out with were more than happy to see him,” she said. “They asked had he been quarantined, but if we were sitting in a restaurant, obviously he did not have to be quarantined.” His 21 days of monitoring himself for symptoms ended Oct. 20.

Since his return, Schnabel said he feels relief from the exhausting, long days of field work. But his most intense emotion is guilt.

“I worked very closely with Sierra Leoneans, the minister of health and people working very hard and very dedicated,” Schnabel said. “The situation there is still dire. I feel guilty I get to go home and they have to continue with the struggle.”