New York (CNN) -- A Doctors Without Borders physician who recently returned to New York from West Africa has tested positive for the Ebola virus, a law enforcement official briefed on the matter told CNN.
The doctor, identified as Craig Spencer, 33, came back from West Africa about 10 days ago, and developed a fever, nausea, pain and fatigue Wednesday night.
The physician, employed at New York's Columbia Presbyterian Hospital, has been in isolation at Bellevue Hospital in Manhattan since Thursday morning, the official said.
At a news conference Thursday, New York Mayor Bill de Blasio sought to allay public concerns about the spread of the deadly virus, saying that "careful protocols were followed every step of the way" in the city's handling of the case. The hospitalized doctor has "worked closely" with health officials, the mayor said.
Spencer posted this image to Facebook on September 18 from Brussells, saying "Off to Guinea with Doctors Without Borders (MSF). Please support organizations that are sending support or personnel to West Africa, and help combat one of the worst public health and humanitarian disasters in recent history."
The doctor exhibited symptoms of the Ebola virus for "a very brief period of time" and had direct contact with "very few people" in New York, de Blasio told reporters.
On his Facebook page, Spencer posted a photo of himself in protective gear. The page indicates he went to Guinea around September 18 and later to Brussels in mid October.
In a statement, Columbia Presbyterian Hospital said the doctor was "a dedicated humanitarian" who went to "an area of medical crisis to help a desperately underserved population."
"He is a committed and responsible physician who always puts his patients first," the hospital statement said. "He has not been to work at our hospital and has not seen any patients at our hospital since his return from overseas."
The CDC had people packing up to go to New York on Thursday, and a specimen from the physician was to be sent to Atlanta for testing, an official familiar with the situation told CNN's Elizabeth Cohen.
Investigators took the case seriously from the outset because it appeared the doctor didn't quarantine himself following his return, the law enforcement official said. The doctor traveled to Brooklyn and then back to Manhattan on Wednesday night, the official said.
In a statement Thursday, Doctors Without Borders confirmed that the physician recently returned from West Africa and was "engaged in regular health monitoring." The doctor contacted Doctors Without Borders Thursday to report a fever, the statement said.
The law enforcement official said the doctor was out in public. Authorities also quarantined his girlfriend, with whom he was spending time since his return from Africa.
The doctor began feeling sluggish a couple of days ago, but it wasn't until Thursday, when he developed 103-degree fever, that he contacted Doctors Without Borders, authorities said.
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