A health care worker who recently returned from West Africa tested positive for the Ebola virus in New York City Thursday.
The man, confirmed by CBS News as Dr. Craig Spencer, 31, worked with the aid group Doctors Without Borders.
Spencer had quarantined himself after coming down with a fever and abdominal pains and was later transported to Bellevue, one of eight hospitals in New York State with specialized Ebola units.
Bellevue confirmed earlier Thursday that Spencer was being tested for the virus.
Those tests came back positive Thursday night, multiple sources confirmed to CBS New York.
Spencer, who works in emergency medicine at Columbia-Presbyterian Hospital, is believed to have treated Ebola patients in Guinea, the station reports.
What makes this case different from other cases that have turned out to be false alarms is that this patient reportedly returned from West Africa within the last two weeks, according to CBS News chief medical correspondent, Dr. Jon LaPook. That is the time symptoms most often begin to appear and Spencer is showing some of those symptoms.
Initially, Spencer contacted officials at Doctors Without Borders Thursday morning to report a fever, complying with the organization's protocols.
"As per the specific guidelines that Doctors Without Borders provides its staff on their return from Ebola assignments, the individual engaged in regular health monitoring and reported this development immediately," said Doctors Without Borders spokesman Tim Shenk in a statement.
Spencer called 911 after after reporting he had a 103-degree fever and diarrhea, city officials said. He quarantined himself and was taken from his apartment in Upper Manhattan, WCBS reported. An EMS crew, wearing specialized suits, picked him up at around noon.
New York health officials will also be tracing the patients contacts to determine if there is any additional risk, the hospital said. There is currently no confirmation that Spencer has contracted the virus.
Mayor Bill de Blasio said Spencer was believed to have been back from Guinea for a very short time and the contacts he had with people were limited.
"Our understanding is there were very few people he had come into contact with," said de Blasio at a press conference.
De Blasio said the doctor was in good shape and has described in great detail where he was in the last few days and with whom he had contact. The mayor said no one else had been quarantined.
Columbia-Presbyterian issued a statement describing Spencer as a "dedicated humanitarian," adding he has not treated any patients at the hospital.
"He is a committed and responsible physician who always puts his patients first," the 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."
Preliminary test results are expected in the next 12 hours, according to a statement from Bellevue.
Only three people have been diagnosed in the U.S., and one has died: a Liberian man in Dallas. The two others, the nurses who cared for the man, are receiving treatment for the disease.