ENGLEWOOD, Colo. – What coach Vance Joseph has called a “flu bug" now has cut an even bigger swath through the Denver Broncos depth chart this week.

Three players who are formally listed as questionable for Sunday’s game against the Miami Dolphins – linebacker Shane Ray, linebacker Todd Davis and linebacker/defensive end DeMarcus Walker – all missed practice time this week due to illness. Ray has missed multiple days this week with the illness.

“It’s obviously spreading fast," Joseph said.

Vance Joseph has no answer's for a flu outbreak that is taking a toll on his team as it heads for Miami. Mitchell Leff/Getty Images

Defensive end Shelby Harris missed Wednesday’s practice with the illness while nose tackle Domata Peko missed two days’ worth of practices leading up to last Sunday’s game Oakland as well.

The illness, which has kept the team’s medical staff busy as other players who have not missed practice time have struggled with it, is another difficult issue in a season full of them for the Broncos. The team will leave for Florida on Friday afternoon and practice in the Miami area on Saturday.

Joseph gave a I’m-not-a-doctor answer when asked Friday after practice what he could do to slow the impact of the illness.

“You’re asking a football coach about flu symptoms," Joseph said with a laugh. “Wash your hands, drink plenty of fluids, right? That’s what I would recommend. I would sign off on that."

Quarterback Trevor Siemian, who will make his eighth start of the season Sunday against the Dolphins, has been one of the players battling the illness, but he did not miss practice time. Siemian said earlier in the week that “a couple of us got it, we'll be all right."

Four players were formally ruled out for Sunday’s game as well. Joseph said Peko (knee), defensive end Derek Wolfe (neck), quarterback Paxton Lynch (ankle) and guard Ron Leary (back) will not play against the Dolphins.

Wolfe said during a local radio appearance earlier in the week that he has experienced numbness in his face and leg after leaving last Sunday’s game in Oakland in the first quarter. Joseph said after Friday’s practice no decision had made about whether to put Wolfe on injured reserve.