US Defence Secretary Lloyd Austin tested positive for Covid-19 on Sunday with mild symptoms, but would retain all authorities as he quarantined at home for the next five days. News of Austin’s infection comes as the Pentagon last week tightened restrictions at its headquarters over concern about the highly transmissible Omicron variant that has led to a sharp increase in Covid-19 cases throughout the world. The military is faced with the challenge of maintaining combat readiness for troops, often in close quarters on ships and planes. Austin, who is vaccinated and has received a booster, said in a statement he last met President Joe Biden on December 21, more than a week before he started experiencing symptoms. “As my doctor made clear to me, my fully vaccinated status – and the booster I received in early October – have rendered the infection much more mild than it would otherwise have been,” Austin added. Austin said he requested a test earlier on Sunday after having symptoms while at home on holiday. He was last at the Pentagon on Thursday. Teacher tests positive for Covid-19 mid-flight, isolates in toilet for 5 hours Austin is one of the most senior members of Biden’s administration to test positive for Covid-19. In October, Homeland Security Secretary Alejandro Mayorkas was diagnosed with the virus. US authorities registered at least 346,869 new coronavirus on Saturday, according to a Reuters tally. The death toll from Covid-19 rose by at least 377 to 828,562. “To the degree possible, I plan to attend virtually this coming week those key meetings and discussions required to inform my situational awareness and decision making. I will retain all authorities,” Austin said. He added that his deputy, Kathleen Hicks, would represent him in some matters. “I continue to encourage everyone eligible for a booster shot to get one. This remains a readiness issue,” Austin said. Top US infectious disease expert Anthony Fauci said on Sunday there was still a danger of a surge in hospitalisation due to a large number of coronavirus cases even as early data suggests the Omicron variant is less severe than other strains. The Omicron variant was estimated to be 58.6 per cent of the coronavirus variants circulating in the US as of December 25, according to data from the Centers for Disease Control and Prevention (CDC). Fauci added that the CDC will soon be coming out with a clarification on whether people with Covid-19 should test negative to leave isolation, after confusion last week over guidance that would let people leave after five days without symptoms.