NEW YORK -- Dr. Craig Spencer, the physician now being treated for Ebola in New York City, is the kind of globe-trotting do-gooder who could walk into a small village in Africa and, even though he didn't know the language, win people over through hugs alone, according to people who worked with him.

Even before leaving for Guinea this summer to fight Ebola with Doctors Without Borders, the 33-year-old had amassed an ordinary man's lifetime worth of world travel, much of which was in the service of the poor.

In the past three years alone, Spencer, an attending physician at New York-Presbyterian Hospital/Columbia University Medical Center, had been to Rwanda to work on an emergency care teaching curriculum, volunteered at a health clinic in Burundi, helped investigate an infectious parasitic disease in the Democratic Republic of Congo and travelled to 32 villages in Indonesia to do a public health survey.

"He was never afraid of getting his hands dirty or his feet dirty," said Dr. Deogratias Niyizonkiza, founder of Village Health Works, the aid group that brought him to Burundi for four months in 2012.

"He went into this environment, a country that is truly off the mark, without knowing the language and he would make everyone feel so comfortable. It's really a daunting task and yet he helped the people immensely," Niyizonkiza said. "He talked to everyone, including the people working in the lab ... Their language was just to hug each other and smile."

In between it all, Spencer ran the ING New York City Marathon in 2013, finishing with a respectable amateur time of 3 hours, 43 minutes.

Ebola survivor Ashoka Mukpo, who was successfully treated in the U.S. after contracting the virus while working in Liberia as a freelance cameraman for NBC, said Saturday that Spencer is a hero.

In an interview with The Associated Press, Mukpo took issue with those who would criticize the doctor for going out in public after returning from West Africa and said there's no evidence Spencer exposed anyone in New York to any risk.

"Dr. Spencer risked his life to treat and lend a hand to people who have very little ability to take care of this problem themselves," Mukpo said from his family's home in Rhode Island. "Before we look at what the implications of this case are, I think we need to honour what he did in West Africa and give him the respect he deserves."

Spencer was hospitalized at New York City's Bellevue Hospital Center on Thursday, six days after returning from Guinea. Health officials said he began feeling tired on Tuesday, spent a day out in the city on Wednesday, and then alerted authorities when he developed a fever Thursday morning.

Experts have repeatedly assured the public that there is little chance that Spencer spread the virus prior to developing symptoms, but his case prompted the governors of New York, New Jersey and Illinois on Friday to order a mandatory quarantine for any arriving international travellers who had contact with Ebola patients in three West African countries -- Guinea, Liberia and Sierra Leone.

The first person to be quarantined under the order was a health care worker arriving at Newark Liberty Airport in New Jersey on Friday after treating Ebola patients in West Africa. By Friday evening, she had developed a fever but tested negative for Ebola in a preliminary evaluation at University Hospital in Newark where she remains under observation and in isolation, New Jersey officials said.

New York Gov. Andrew Cuomo criticized Spencer, saying he should have stayed home until any danger period for the disease had passed. The virus can hide in the body for up to 21 days before a person develops symptoms.

"Dr. Spencer is a valued fellow and was a volunteer and did great work, but that was a voluntary quarantine situation for 21 days. He's a doctor and even he didn't follow the voluntary quarantine, let's be honest," Cuomo said.

Neither the U.S. Centers for Disease Control nor Doctors without Borders ask health care workers returning from the Ebola hot zone to quarantine themselves, but they do recommend that they monitor their temperature at least twice a day. Spencer was complying with that guidance, officials have said. International aid groups have warned that such restrictions could deter health care volunteers from travelling to West Africa.

Friends of the stricken doctor described him Friday as fun-loving but driven to stay involved in the global health fight.

"Everything else in his life was two, three and four on the priority list," said Dr. Liz Edelstein, a San Diego emergency medicine physician who met Spencer while teaching a course on wilderness medicine.

Doctors at Bellevue and city officials haven't released much information about Spencer's condition, but said he was well enough on midday Friday that he was speaking to people by cellphone.

Spencer's fiancee has also been quarantined at the hospital, though she had not developed any sign of the illness.

In an article that appeared in the journal of Emergency Physicians International last May, Spencer talked about some of the tough conditions he witnessed while working in Burundi. Those included a lack of basics as simple as aspirin, and having to ration a limited supply of oxygen for the gravely ill.

"In one case we gave oxygen to a child with pneumonia over a woman who was very anemic from malaria," he said. "The physicians in Burundi are some of the best I've ever come across ... I don't think I would have had the same success in deciding who needed oxygen to survive and who didn't. But they had experience. They'd seen it before."

Columbia University Mailman School of Public Health epidemiologist Leslie Roberts, who worked with Spencer on field research in Burundi, said in an email that he is "one of the most brilliant and delightful people" he'd ever worked with.

Spencer attended The Johns Hopkins University as an undergraduate, studied Chinese language and literature at Henan University, got his MD at Wayne State University School of Medicine, in Detroit, and his Masters in public health at Mailman, according to his LinkedIn page. His profile said he was also proficient in Spanish, French and Greek.

Colleagues in Guinea said Spencer conscientiously followed safety procedures in place at the Doctors Without Borders clinic in Gueckedou.

"I'm asking myself how he got the virus because he was a rigorous man," said a hygienist, one of two staffers who spoke to The Associated Press on condition of anonymity because they were not authorized to talk to the press.

"Since we learned that he was infected, we've had low morale," the hygienist said. "We are praying for Craig and for ourselves because we rub shoulders with death every day."