The number of crew on the USS Theodore Roosevelt who have tested positive for the coronavirus has risen 13 per cent in the past 24 hours to 155, two days after the aircraft carrier's captain was dismissed for raising concerns about the outbreak on board.

Captain Brett Crozier was relieved of his command after warning superiors about the danger of Covid-19 spreading among his crew – a message that was then leaked to the San Francisco Chronicle.

He wrote: "We are not at war. Sailors do not need to die. If we do not act now, we are failing to properly take care of our most trusted asset – our Sailors."

He added: "Decisive action is required. Removing the majority of personnel from a deployed US nuclear aircraft carrier and isolating them for two weeks may seem like an extraordinary measure.

"This is a necessary risk. It will enable the carrier and air wing to get back underway as quickly as possible while ensuring the health and safety of our Sailors. Keeping over 4,000 young men and women on board the TR is an unnecessary risk and breaks faith with those Sailors entrusted to our care."

The acting Secretary of the Navy, Thomas Modly, relieved him of his duties as a result, saying he had shown poor judgement by circulating the memo to up to 30 people.

However, Capt Crozier was given a standing ovation by his crew, who chanted his name as he left the ship for the last time on Friday.

Mr Modly told the Reuters news agency that Capt Crozier could still face disciplinary action. More than 120,000 people have signed a petition calling for his reinstatement.

The great-grandson of President Theodore Roosevelt, for whom the nuclear-powered aircraft carrier is named, wrote in the New York Times that his distinguished forebear would have approved of the captain's actions.

Tweed Roosevelt wrote that in 1898 his ancestor found himself in the same position during a yellow fever and malaria outbreak in Cuba, where he was commanding a voluntary cavalry outfit called the Rough Riders. Roosevelt wrote a letter to the then Secretary of War demanding action – and was refused a Medal of Honor as a result.

In his op-ed the younger Mr Roosevelt writes: "In this era when so many seem to place expediency over honor, it is heartening that so many others are showing great courage, some even risking their lives. Theodore Roosevelt, in his time, chose the honorable course. Captain Crozier has done the same."