Friends old, from Michigan, and relatively new, from New York City, where Dr. Spencer is an attending physician at NewYork-Presbyterian Hospital/Columbia University Medical Center, described a singularly driven man who, while easygoing and friendly, possessed an unshakable belief in where he belonged — often in harm’s way.  In field exercises in wilderness medicine classes that Dr. Spencer helped run in the Adirondacks, he was the instructor who took playing the role of victim most seriously, using makeup and props to make a fake wound look more convincing.  “Craig lying in the brambles, covered with blood in a scary injury that we made up for him,” said Dr. Jay Lemery, who worked on the same trips. Students would cry out in surprise before kneeling to work on him.  Rehearsing in the woods, however, was a world away from the real thing, even for doctors trained in international medicine.  “Truthfully, when Ebola’s on the table, it’s very easy to look the other way,” Dr. Lemery said. “Really, if there’s a gut check, I’m not sure a lot of us are able to do that.”  Dr. Spencer grew up in a modest house on the outskirts of affluent Grosse Pointe. The middle child of three, Dr. Spencer went the furthest, studying his way through college and medical school while his siblings, a younger sister and an older brother, stayed behind. “He was always the brainiac, always had his nose in a book,” Mr. Cedar said. “He had all the options to do wrong and he didn’t. He had the options to go out and booze on a Friday night just like everyone else, but he never did.”  In Mr. Cedar, Dr. Spencer found an outlet for another passion. Mr. Cedar, being from Canada, had for years studied French, one of several languages his friend was learning. “He was always speaking French when we hung out,” Mr. Cedar said. “The kid speaks like 20 languages.”  Or at least four, according to a biography Dr. Spencer posted online, including Spanish and Chinese. Role-playing a hurt patient in the woods, Dr. Spencer was known to pretend not to understand English to heighten the difficulty of diagnosing his injury.  Kate Calabresa Murray, a former teacher at Grosse Pointe North, now its principal, recalled that Dr. Spencer stood out.  He had “maturity beyond his years and selflessness beyond his years,” she said. A counselor, Barbara Skelly, said he knew at the time that he wanted to be a doctor, and took the appropriate science classes he thought he needed to get there.  He was an avid hockey player, playing forward. “He was cool with the jocks, and he was cool with the nerds,” Mr. Cedar said. After graduation, though, “he kind of disappeared.”  Another high school friend, Charles Dallas, went to college with Dr. Spencer and tried to persuade him to join a fraternity. “He was too focused on studying,” Mr. Dallas said.  Dr. Spencer graduated from the Wayne State University School of Medicine in Detroit and went on to earn a master’s degree in public health at Columbia University’s Mailman School of Public Health. He traveled to China, where he studied Chinese at Henan University. It was there, he told Mr. Cedar later, that he met “the girl I love,” Morgan Dixon. The two were recently engaged to be married, planning a September 2015 wedding in a park on the Detroit River.  The couple shared an apartment in Harlem, with Dr. Spencer moving with equal ease in two very different worlds, from the impoverished conditions of South Africa to the hipster hangouts of his home.  He traveled to Rwanda, Burundi and the Democratic Republic of Congo, among other places. Dr. Elizabeth Edelstein, an emergency physician in San Diego, knew him from New York and often invited him to lecture at wilderness medicine seminars she led. Sometimes he did, but other times, he demurred. “He’d love to come out and teach, but he couldn’t make the commitment because he might be in Africa,” she said.  In September, he traveled with Doctors Without Borders to an Ebola treatment center in Guéckédou, Guinea, a dusty town of muddy roads and open-air markets still bearing the scars of the civil war in Sierra Leone in the 1990s.  He worked as a doctor, seeing patients, and as an epidemiologist, a colleague at Doctors Without Borders said on the condition of anonymity because the group told its doctors not to speak on the matter. There are 90 beds at Guéckédou, including 15 for suspected cases. The treatment center is on the grounds of the main government hospital in the center of town, on top of a hill, a collection of worn buildings and the now-familiar sight of tents alongside them.  The center, largely empty of patients as recently as July, is now full.  He boarded a plane to leave Guinea on Oct. 14. A friend joked on Facebook: “Watch out for the Ebola!” But with the jokes came deep concern for Dr. Spencer’s safety. “We can honestly say we’ll be so happy when Craig returns to the States,” his mother, Pat Casey-Spencer, wrote on Facebook, according to Mr. Cedar. “We admire compassion to help the sick but we’ve never wanted him home more so now than ever.” She called Ebola “so devastating.”  He arrived at Kennedy International Airport on Oct. 17. His every movement since shortly after that jet touched down is now facing intense scrutiny.  On Tuesday, feeling fatigue, Dr. Spencer nonetheless visited the Greenwich Village restaurant the Meatball Shop for about 40 minutes before walking uptown on the High Line, stopping at the Blue Bottle Coffee stand along the way. He exited the park around 5:30 p.m. and took a No. 1 train toward home.  The next day, his tour of young, cool New York continued to play out, as he picked up his food from a community farm-share program and, later, traveled by subway to a Brooklyn bowling alley, the Gutter. After the diagnosis of Ebola was made, his activities were widely criticized on social media and television news programs. In remarks on Friday, even Gov. Andrew M. Cuomo of New York suggested he should have behaved as if under quarantine. How, people asked, could a doctor just back from treating Ebola victims ride mass transit and go bowling?  Those comments outraged Dr. Spencer’s friends. “He would never do anything to put anyone at risk, ever,” Mr. Cedar said. It was unclear what Dr. Spencer knew of the backlash; one friend said that, following Dr. Spencer’s expressed wishes, he would decline to comment.  Dr. Spencer did communicate with his fiancée, Ms. Dixon, on Friday, said a mutual friend, Shalva Wise, 31. She said that when Dr. Spencer reported having a fever of 100.3 degrees on Thursday, he was being cautious, using a lower threshold for Ebola testing. The Centers for Disease Control recently lowered the threshold for suspecting a case of Ebola from 101.5 degrees to 100.4, which Dr. Spencer was just under when paramedics arrived at his apartment.  “He has really done everything he can,” Ms. Wise said.  He seems to have maintained some strength and energy as his body fights the virus.  “Morgan said, ‘He called me this morning and said, ‘I already have done yoga,’ ” Ms. Wise said. “He woke up and stretched. That’s what he does.”  A version of this article appears in print on October 25, 2014, on Page A17 of the New York edition with the headline: Ebola Patient in New York Is Called a Doctor at Ease in Danger. Order Reprints| Today's Paper|Subscribe
Friends and former classmates of Dr. Craig Spencer, who tested positive for Ebola in New York, described him as driven and with an unshakable belief in helping others no matter the place.