President Donald Trump on Monday left the hospital where he has been treated for Covid-19 and boarded a helicopter to return to a White House hit by a wave of infections and a campaign further shadowed by the pandemic four weeks before Election Day.

Wearing what appeared to be a white surgical mask, Trump pumped his fist and gave a thumbs up as he walked down the steps of the Walter Reed Medical Center outside Washington, responding to a reporter’s question about how many people were infected at the White House by saying: “Thank you very much.”