Manager Aaron Boone said Happ is no longer contagious. Assuming everything goes well over the next couple of days, Happ is on track to start Thursday against Texas in the opener of an 11-game homestand.
"He's out of the woods, virus-wise," Boone said before New York's game against the Chicago White Sox.
Happ came over in a July 26 trade with Toronto for infielder Brandon Drury and minor league outfielder Billy McKinney. He pitched six crisp innings in a win against Kansas City in his New York debut, but the illness took him out of a critical four-game series in Boston, where the Yankees were swept by the major league-leading Red Sox.
Happ, who turns 36 in October, is 11-6 with a 4.05 ERA in 21 starts this year.
The wild card-leading Yankees arrived in Chicago early Monday morning after a difficult 5-4 loss at Fenway Park. New York carried a 4-1 lead into the ninth, but Boston rallied against All-Star closer Aroldis Chapman and Andrew Benintendi hit a game-ending RBI single off Jonathan Holder in the 10th.
They responded with a 7-0 victory against the White Sox, stopping a season-high five-game slide. They improved to 16-15 in their last 31 games.
"Look, we know we're really good,'' Boone said, "and the guys I don't think have any doubt in there. I think, to a man, they understand what we're capable of.''
Miguel Andujarserved as the designated hitter a day after he committed two errors against Boston, running the total for the rookie third baseman to 10 in 92 games in the field. But Boone said he had planned on starting Neil Walker at third for the opener against the White Sox.
"Miguel I feel like is equipped to deal with the successes and failures that you inevitably have up here, so I don't worry about putting him back out there,'' Boone said before the win.