US defence secretary Lloyd Austin said he tested positive for Covid-19 on Sunday with mild symptoms and would attend meetings virtually as he quarantined at home for the next five days.

News of Austin’s positive test comes after 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 infections throughout the world.

The military is faced with the challenge of maintaining military readiness for troops, often in close quarters on ships and planes. Austin, who is fully vaccinated and received a booster in early October, said in a statement he last met President Joe Biden on December 21.