Mannarino was docked $2,500 for unsportsmanlike conduct, and Thiem was fined $1,500.
Mannarino has acknowledged he is part of a group of players who were in contact with Benoit Paire, the only US Open entrant to test positive for the coronavirus so far. That group was placed under additional restrictions in case they might have been exposed to the virus by Paire.
The U.S. Tennis Association specified that Thiem's entourage violated the rule requiring universal masking. There was no further explanation.