At least three people who came into contact with Craig Spencer—the doctor who tested positive for Ebola Thursday night after returning from Guinea—have been placed into isolation. The New York City health department said in a statement yesterday that disease detectives are currently working to retrace Spencer's every step in the days leading up to his diagnosis.

According to the New York Times, Spencer's fiancée has been placed into isolation at Bellevue Hospital; two others he came into contact with Tuesday and Wednesday have been told they will be placed into quarantine. None of them have shown signs of illness, the paper reports.

Almost as soon as the Spencer's diagnosis was announced, New York City Mayor Bill de Blasio and New York Governor Andrew Cuomo have been working overtime to assuage public fears of the virus spreading further—especially after news broke that Spencer had taken at least three subway lines (the A, 1, and L) in the past week.

"There is no reason for New Yorkers to be alarmed," de Blasio said at a news conference. "Being on the same subway car or living near someone with Ebola does not in itself put someone at risk."

The Times reports that New York City health officials had been preparing for Ebola to eventually reach the city "for months."

"From a public health point of view, I feel confident that we're doing everything that we should be doing, and we have the situation under control," Cuomo said at the same press conference.

[Image via AP]