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.”

The Republican president, running for re-election against Democrat Joe Biden in the November 3 US election, was admitted to the hospital on Friday after being diagnosed with the disease caused by the novel coronavirus.

“Feeling really good!” he said on Twitter earlier. “Don’t be afraid of COVID. Don’t let it dominate your life. We have developed, under the Trump Administration, some really great drugs & knowledge. I feel better than I did 20 years ago!”

The disease has killed more than 1 million people worldwide and more than 209 000 in the United States alone — the highest death toll of any country.

Trump, 74, has not had a fever in more than 72 hours and his oxygen levels are normal, his medical team told reporters in front of the hospital.

The doctors declined, however, to discuss any toll the disease could have on the president’s lungs or disclose when Trump last tested negative for the coronavirus.

The team added that the President had received supplemental oxygen twice in recent days.

“He may not entirely be out of the woods yet,” Dr. Sean. P. Conley, the White House physician, said. “If we can get through to Monday with him remaining the same or improving, better yet, then we will all take that final, deep sigh of relief.”

However, Conley said the medical team believed Trump was ready to leave the hospital, stressing he would have world-class medical care around the clock at the White House.

Conley said doctors were in “unchartered territory” because Trump had received certain therapies so early in the course of the illness.