A military hospital ship which arrived in New York City on Monday is fighting to stay in a coronavirus-free "bubble" so as not to risk bringing the disease on board, its medical officer said.The 1,000-bed USNS Comfort, previously deployed to conflict and natural disaster zones, was sent to Manhattan to ease the strain on health centers in the city at the epicenter of America's outbreak by caring for patients other than those diagnosed with the virus. By Friday it had received 21 patients, according to the ship's press officer Lieutenant Commander Amelia Umayam. "We consider the USNS Comfort to be in a bubble," said medical officer Captain Patrick Amersbach as he explained the procedures followed by the ship's crew to shield it from the virus, including not disembarking for as long as it is docked.Patients are arriving directly from New York hospitals and will be screened in advance to make sure they are free of the coronavirus. For the time being, even relatives of patients are not allowed to board the ship, though Amersbach said a protocol for loved ones to visit was being put in place "because nobody wants to be without their family members."If a worker needs to board the ship to perform installations or repairs, they must be examined, wash their hands in front of a witness, and put on a mask before being escorted to the precise location on the ship where they will work.Once finished, they will be escorted directly off again.New York City has had more than 57,000 positive coronavirus cases since the arrival of the pandemic and 1,867 deaths. The nearby Javits Center, which has been converted into a field hospital by the US military and was not originally intended to house coronavirus patients, will now do so.But there are no plans for the USNS Comfort to make such a move. "We're going to try and stay in that bubble," said Amersbach.