The 42-year-old is experiencing mild flu-like symptoms and tested positive Friday evening, Politico reported.
Stepien now becomes the fourth person on the White House’s debate prep team to test positive for the virus.
The others are Kellyanne Conway, who announced Friday night that she was infected, Hope Hicks, whose COVID-19-positive status was announced Thursday, and Trump himself, who remained Saturday morning at the Walter Reed National Military Medical Center in Bethesda, Md.
Stepien had also reportedly traveled to the presidential debate on Air Force One with Trump and Hicks.
He will continue to lead the campaign while working remotely under quarantine, according to Politico.
Trump’s doctor late Friday said in a statement that the president was doing “very well” and “resting comfortably.”
“Going well, I think!” Trump added in a tweet just after 11:30 p.m.
At least five of those infected around Trump had attended a tightly packed, mostly maskless Rose Garden ceremony for the president’s Supreme Court nominee, Amy Coney Barrett.
They are the first lady, two Republican senators who sit on the Senate Judiciary Committee, the president of Notre Dame University — where Barrett taught and had attended college — and Conway.