The US naval commander whose widely publicised plea for help for his coronavirus-affected crew led to his dismissal has reportedly himself tested positive for the disease.Captain Brett Crozier's Covid-19 test result was reported on Sunday by the New York Times, just hours after US Defence Secretary Mark Esper defended the captain's firing.LIVE | SA coronavirus cases at 1 655, US sees over 1 200 deaths in 24 hoursEsper told ABC that Navy Secretary Thomas Modly had "made a tough decision, tough call" in deciding to fire Crozier from his command of the aircraft carrier USS Roosevelt, now docked in Guam.Asked about a report that US President Donald Trump wanted Crozier fired, Esper replied: "This was the secretary's call. He came and briefed me... It was the secretary's call. I told him I would support it."The firing was widely condemned as a callous and unfair punishment of a respected officer who was looking out for the welfare of his crew when he implored his superiors to let him quickly vacate the ship after it docked in Guam."We are not at war," Crozier wrote in a letter that leaked to the press. "Sailors do not need to die."'Extremely poor judgement'But some senior Pentagon officials said Crozier erred by letting his plea go public.Crozier "demonstrated extremely poor judgement in the middle of a crisis", needlessly worrying family members and undermining the chain of command, Modly said.Trump, speaking in a news conference on Saturday, supported the dismissal."He shouldn't be talking that way in a letter," he said of Crozier. "I thought it was terrible what he did."The Times, in reporting Crozier's test result, cited two of his former classmates at the US Naval Academy. It said he had begun exhibiting symptoms before leaving the ship on Thursday.Hundreds of sailors cheered Crozier as he left the ship, as seen in video that quickly went viral. Some called him a hero.Democrats have also sharply criticised the dismissal.Joe Biden, the leading Democratic candidate for president, condemned the firing on Sunday, telling ABC it was "close to criminal"."I think he should have a commendation rather than be fired," the former vice president said.And a statement from Democratic leaders of the House Armed Services Committee said Crozier might not have handled the matter perfectly, but that his dismissal was an "overreaction".Esper declined on Sunday to say whether other Pentagon leaders agreed with the firing, pointing to an ongoing investigation.He told CNN that more than half the Roosevelt's 4 800-member crew had now been tested for the coronavirus. In all, 155 sailors tested positive but none required hospitalisation, he said.Crozier's dismissal came as the Pentagon struggles, amid the spreading pandemic, to maintain the readiness of its air, sea and ground forces worldwide."We have had to cancel exercises. We've had to constrain basic training, for example," Esper said, before adding, "We think those are all manageable."