The US navy has dismissed the commander of the USS Theodore Roosevelt aircraft carrier, who had raised the alarm about an outbreak of coronavirus on his ship.

Thomas Modly, the acting secretary of the navy, said that Captain Brett Crozier had been relieved of his command of the nuclear-powered carrier because he had copied in too many people on an internal memo on Monday, in which he urgently appealed for members of his crew who had fallen ill to be allowed to disembark for medical care in Guam.

By Thursday, 114 of the more than 4,000 crew had tested positive for Covid-19. Modly did not accuse Crozier of leaking the memo, but suggested he made it more likely that the letter would be leaked. He also accused Crozier of raising unnecessary alarm among the sailors’ families, and exaggerating the threat to their lives.

“We are not at war. Sailors do not need to die,” Crozier wrote in his four-page 30 March memo to senior officers, which was reported by the San Francisco Chronicle. “If we do not act now, we are failing to properly take care of our most trusted asset – our sailors.”

Democratic presidential candidate Joe Biden said the Trump administration’s decision to remove the commander showed “poor judgement”.

In his letter, Crozier said it was impossible to achieve social distancing and quarantine conditions on board the Roosevelt, and therefore the majority of the sailors on board should be disembarked for quarantine and treatment.

Briefing the press on his decision on Thursday, Modly said accused Crozier of “not being careful” about who would receive his note.

“It was copied to 20 or 30 other people. That’s just not acceptable. He did not take care and what that did is it created a little bit of a panic on the ship,” Modly said. He stressed that he was not accusing Crozier of leaking the memo himself.

Modly said that the navy had already begun mobilizing resources to help the crew in response to Crozier’s earlier requests for assistance.

“He was fully aware of the navy’s response, only asking that he wished the crew could be evacuated faster,” the acting secretary said. He pointed out that so far, none of the infected crew was so ill to need hospitalization, and contrasted that with Crozier’s warning that sailors could die.

“No one knows that to be true. It does not comport with the data we have right now on the ship,” Modly said.

He argued he was forced to act “when I have a commanding officer who’s responsible for a nuclear powered aircraft carrier, with all that lethality and all that responsibility, who exercises that poor judgment in a situation in a crisis like this.”

Modly and other officials had initially said that Crozier was right to air his concerns. On Thursday the acting secretary denied he had been under pressure from the White House to fire the commander.

The Democratic leadership of the House armed services committee issued a statement saying that Crozier had not behaved “appropriately” but argued the dismissal was “an overreaction”.

“It is a destabilizing move that will likely put our service members at greater risk and jeopardize our fleet’s readiness,” the statement read.