Stepien is expected to work from home in quarantine.
Stepien replaced former campaign manager Brad Parscale in July. The 42-year-old Stepien was previously the campaign's deputy manager. For Trump's 2016 campaign, he had served as a senior political adviser and a national field director. Stepien later served as a White House political director in the Trump administration.
Prior to working under Trump, Stepien worked for former New Jersey Gov. Chris Christie as manager for Christie’s gubernatorial campaigns in 2009 and in 2013. He also worked for other New Jersey Republican politicians prior becoming involved with Christie’s campaign.
White House press secretary Kayleigh McEnany said in a statement on Friday that Trump will be working from the presidential offices at Walter Reed over the next few days "out of an abundance of caution." She also said that Trump "remains in good spirits, has mild symptoms, and has been working throughout the day."
Stepien was known to have been with the president on Air Force One flying to and from Cleveland, Ohio, for the first presidential debate. White House aide Hope Hicks was also aboard the aircraft on Sept. 29.