Since the end of November NFL facilities are closed Monday and Tuesday for teams that played on Sunday. There is the possibility that Kupp wasn't contagious on Sunday and hasn't been in contact with anyone from the team since then. (He was put on the COVID list Tuesday so I'm pretty sure he's been quarantining at least since then.)
From [
www.espn.com] :
Team facilities will be closed to all in-person activities Monday and Tuesday, the NFL said Friday in a leaguewide memo.
The ban does not apply to teams scheduled to play on Monday or Tuesday.
AlbaNY_Ram