New York City Mayor Bill de Blasio and other local officials moved to calm Ebola fears at a press conference at Bellevue Hospital after doctor Craig Spencer, who returned from a trip to Guinea on Oct. 17, tested positive for the Ebola virus.

What we know, from city and health officials:

— Spencer went to Guinea in West Africa as part of the humanitarian organization Doctors Without Borders to help health care efforts in the Ebola-ravaged region. He returned on Oct. 17, traveling through Kennedy Airport.

— On Thursday Oct. 23 he came down with a 100.3-degree fever and nausea and was taken by ambulance to Bellevue Hospital by a specially trained team in protective suits.

— According to Mary Bassett, the city's health commissioner, Oct. 23 was the first day he showed any symptoms, though he did report feeling tired on Oct. 21.

— Four people he came into contact with on Oct. 22 — his girlfriend, two friends and a cab driver — are being monitored, though none are considered at risk, Bassett said.

— Spencer took the A and L subway trains to a Williamsburg bowling alley called The Gutter. Bassett said the bowling alley is closed and the CDC is sending teams  to investigate.

— He also reportedly visited the High Line park in Manhattan, went to a restaurant for dinner, and rode the 1 train and an Uber taxi.

— Spencer's apartment building has been closed, and all tenants have been told to vacate while the CDC investigates.

— Gov. Andrew M. Cuomo said eight hospitals in the state are specially equipped to handle Ebola patients and Bellevue is one of them.

— Mayor Bill de Blasio said, “There is no reason for New Yorkers to be alarmed.”