Stephen McManus was forced to sit out Saturday's 1- 1 draw with Reading after complaining of feeling unwell in the build-up to the game, and Boro's medical staff became concerned when two more players reported similar symptoms on Sunday morning.
With his squad already stretched because of injuries to the likes of Tony McMahon, Willo Flood and Jeremie Aliadiere, Strachan opted to cancel yesterday's training session in an attempt to stop the virus spreading.
And while he is hopeful such decisive action will have prevented further members of his squad from becoming infected, he admits he will not be able to confirm his starting line-up for tonight's game until he sees how many of his players are able to rise from their sick bed.
They came in for a bit of a warm down on Sunday, but there's a virus going around the club so I felt I had to give everyone the day off (yesterday) to try to make sure it didn't spread, confirmed Strachan.
Stephen McManus was the first player to show signs of suffering, but another one or two already seem to have picked the virus up off him.
We're hoping that by clearing the decks, we're able to get a team for the Preston game.
We'll get everybody to come in on Tuesday, have a bit of a head count and see who's fit enough to play. It's a concern, but we're hoping the virus hasn't spread too far.
While Rhys Williams is available after serving a onematch suspension at the weekend, Strachan's biggest concerns ahead of tonight's game relate to the midfield.
Saturday's central unit contained Middlesbrough's only four available midfielders, and with the deadline for emergency loan signings due to arrive on Thursday, the Scot is hoping to make a lastminute addition to the ranks.
A loan signing might help the players because, in the middle of the park, the same three or four are doing all the work every week, said Strachan.
It wouldn't be so bad, but the pitches are so heavy this year because of the weather that it's taking its toll on a lot of midfield players.
We've been trying to get someone in, but at this stage it's just not been possible. We don't want to bring someone in just for the sake of filling spaces, but midfield is an area where we've basically had three players for the last three games. As a result, those guys have had to work hard.
Ideally, Strachan would like to sign someone with a view to a permanent move in the summer, as a prelude to another radical overhaul of his squad in the close season.
He is expected to sign a new first-choice goalkeeper, despite giving Brad Jones another chance to underline his credentials at the weekend.
Jones, who was a surprise replacement for Danny Coyne, produced a crucial save in each half as Boro extended their unbeaten home run to eight matches, and Strachan admits he shuffled his goalkeeping pack in an attempt to hit on a winning formula.
Danny had done nothing wrong, he said. But sometimes a manager just feels he has to change something to try to get a win.
I did the same when I was Coventry manager with Steve Ogrizovic. I stuck Chris Kirkland in, even though Steve had been one of the better players at the time.
You do things every now and then because you think it might just be the change you need to get a win. We were close to getting that win at the weekend.
Close is not really good enough at the moment though, with Cardiff's weekend win over Watford having left Boro eight points adrift of the play-off places with eight games to play.
A victory tonight is essential if they are to remain in contention, but Strachan admits a run of three successive draws has made a major dent in his side's promotion ambitions.
It's getting harder and harder, he said. And the most annoying thing is, we've made it harder for ourselves.
We've had it in our grasp to climb the table, but we've made it harder to reach the play-offs.
It's frustrating because we've been in the lead in each of the last three games. We've got nobody to blame but ourselves.
MIDDLESBROUGH (probable, 4-4-2): Jones; Naughton, Wheater, McManus, Pogatetz; R Williams, O'Neil, Robson, Arca; Killen, McDonald.
Source: Northern Echo
Source: Northern Echo