“Bringing people onto a ship is inherently risky,” Capt. Patrick Amersbach, commanding officer of the medical personnel aboard the Comfort, said in a telephone interview from the ship. “So we have to be overly cautious.”

But within the striking white and red hull of the Comfort, some of the crew members say they are scared that they are tempting fate by dropping anchor in New York harbor. As of a week ago, the crew had not been informed of the screening procedures for patients coming aboard, other than temperature checks, according to one person aboard the Comfort familiar with the situation.

He added that there was some talk of conducting X-ray examinations — in an effort to check the lungs for evidence of the virus — but it is unclear if those are proceeding.

Navy officials acknowledge that it will be extremely difficult, yet paramount, to ensure no one with coronavirus gets on board. The ship’s crew will not be allowed off the ship; there will be no visits into Manhattan and of course no trips to bars or restaurants for takeout. Ship personnel will be doing temperature checks and scans and are still working on additional ways to screen patients before they are allowed on board, officials said.

With 12 operating rooms, 1,000 hospital beds, radiology services, a laboratory, pharmacy and CT scanner, the Comfort is its own fully-staffed hospital. It responded to the earthquake in Haiti in 2010, and showed up off the coast of New Orleans after Hurricane Katrina hit in 2005. It has even been to New York before, when, in the days after the September 11, 2001, terrorist attacks, the Comfort provided aid and medical help largely for emergency medical workers.

It floated in the Arabian Sea during the Iraq war in 2003, receiving and treating injured Marines and soldiers. Treating combat wounds is its main function. The ship, a refurbished oil tanker that was commissioned in 1987, has never before been involved in a response to an infectious disease pandemic, Captain Amersbach said.