The Mercy will also send about 40 medical staff to a regional skilled nursing facility on Monday, Navy Capt. John Rotruck, the ship's commander, said Wednesday. He added that elderly patients will not be brought to the ship, despite earlier suggestions that could happen.
Rotruck said a plan under discussion would reduce the number of available hospital beds on the Navy ship from 1,000 to 250. Documents reviewed by The AP said the plan could free up medical staff that could then go on to other missions. The ship has 800 active duty doctors, nurses and medical staff members on board.
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Two weeks ago, California officials were planning for a potential surge in coronavirus cases that by mid-May could require adding up to 66,000 additional hospital beds. The Mercy was part of the ramp-up effort, but since then, hospitalizations have leveled off and ample rooms are available.
The ship left San Diego on March 23 and arrived in Los Angeles four days later to provide relief by taking patients who were not infected with the virus.
The facility was designed to remain a strict non-coronavirus zone with protocols for testing patients and staffers.
Many of the worst outbreaks now occurring are in nursing facilities, and some are having staffing issues as workers are infected or stay home.
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Rotruck said there has been no final decision, but 250 beds would be a reasonable size to maintain. He said that "probably in the neighborhood of 100 or more people" could be made available for other missions, as a result of the reduction in beds. He said no decisions have been made on where medical staff may go.
"I'm not surprised if it happens," he said, adding that 51 patients have been treated on the ship since it arrived and 17 were on board as of Wednesday. The ship has seen an average of 20 to 21 people a day.
Reducing the Mercy's capacity, he said, won't hurt its ability to relieve local hospitals. "From the perspective of our partners here in L.A., they won't see any difference in what we're able to do for the local area," he said.
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The changes come as the Mercy works to overcome a small outbreak of the virus. Seven crew members have tested positive, and about 112 were taken off the ship and quarantined because they had contact with someone who tested positive.
There have been no new cases of the virus among the ship's crew since Sunday, Rotruck said, adding that several staff have already been able to return to duty. He said officials have not determined how the virus got on board the ship, but noted that many of the staff came from around the region and could have been carrying the virus but not showing symptoms when they arrived.
Rotruck said the ship will remain in L.A. for as long as needed, and there are no plans right now to leave.
About two weeks ago, a train engineer was accused of intentionally running a train off the tracks at high speed near the Port of Los Angeles in an attempt to crash into the Mercy.
The Pacific Harbor Line train derailed, running through the end of the track and crashing through barriers, finally coming to rest about 250 yards from the docked naval ship. Federal prosecutors allege train engineer Eduardo Moreno, 44, of San Pedro intended to hit the ship, saying he thought it was "suspicious" and did not believe "the ship is what they say it's for.'"
WATCH: Prosecutors: Engineer deliberately ran train off tracks in attempt to smash the USNS Mercy
The Associated Press contributed to this report.