From the Washington Post (emphasis added):
The three service centers, among 10 campuses nationwide where the IRS is trying to reinstate 11,000 employees, had to partially close for a week for deep cleaning. ...
The tax behemoth that touches virtually every American has made the government’s most aggressive effort so far to recall its workforce. But like other federal agencies following President Trump’s order to reopen the country, the IRS is struggling to ensure the safety of its employees as it tries to chip away at a crushing backlog and serve the public. ...
As of Monday, about 3,000 customer-service and clerical workers had volunteered to return to the office, an absentee rate of almost 75 percent. ...