The U.S. Navy hospital ship brought to New York City to help hospitals overwhelmed with the coronavirus pandemic is changing its criteria so it can take on non-COVID-19 cases more quickly.

The 1,000-bed USNS Comfort had only 20 patients as of Thursday night. In the city alone, there are more than 49,000 confirmed cases.

During an appearance Friday on MSNBC's "Morning Joe," New York City Mayor Bill de Blasio said he expects the number of patients on the ship to "change very rapidly."

“I’m sure that ship will be very full soon," he said. "They have to be smart about what cases they take and create a protocol that’s going to work because it’s going to get very busy, very quickly next week. So I’m convinced over the next few days they’ll be prepared and they'll be filling up."

When the ship first arrived in the city on Monday, it was announced that the vessel would only take those who tested negative for the coronavirus.

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But on Friday, the Department of Defense said the screening protocols have been modified and will now occur on the ship's pier "in an effort to reduce the backlog at some of the nearby New York hospitals."

The updated guidelines say that an asymptomatic patient does not need to have a negative coronavirus test before they can be transferred onto the ship. "Each patient will still be screened by temperature and a short questionnaire," the agency said in a press release.

Navy spokeswoman Beth Baker told NBC News that in an effort to keep coronavirus cases off the vessel, screened patients will be isolated and immediately tested for the virus. If a test comes back positive for COVID-19, the patient will be transported to the Javits Center, she said.

The New York City convention center was turned into a medical station and was initially going to treat people who do not have the novel coronavirus. The Department of Defense said Friday that it will now also take patients infected with COVID-19, the disease caused by the virus.

Baker said just like any hospital, the ship is prepared to handle COVID-19 if there were to be any confirmed cases.

"The hospital ship has infection control procedures that will be followed," she said via email. "Additionally, the ship is equipped with appropriate personnel protective equipment. All personnel aboard Comfort practice preventative hygiene measures recommended by the Centers for Disease Control and Prevention to help prevent the spread of COVID-19."

Baker said since the ship arrived, they have worked closely with officials to get non-COVID-19 patients onboard.

"We will continue to coordinate hospital-to-hospital transfer of patients to USNS Comfort," she said. "We are working closely with city and local health officials in the coming days to make sure that we are able to provide the relief valve that we came here to provide."

A second ship, the USNS Mercy, was sent to Los Angeles to help hospitals over there.