The Rovers boss contacted Chelsea and the Premier League before taking his sicksquad to Stamford Bridge on Saturday to voice his concerns about passing on the bug.
He left victims David Dunn and Chris Samba in bed but was still worried the highlycontagious virus could spread.
Bug: Michael Essien and his Chelsea team-mates could have been exposed to swine flu by Blackburn during their clash at Stamford Bridge on Saturday
Worried: Sam Allardyce
Allardyce revealed a third Rovers player has gone down with bug along with a member of the coaching staff and the club doctor.
The Rovers boss said: 'There's no doubt we could have passed it on. If you look at the medical side of it this is a very infectious virus we have.'
Blackburn have already contacted Carling Cup opponents Peterborough,although Allardyce has no doubt the game will go ahead.
Chelsea are confident they took all precautions necessary and Carlo Ancelotti led the training session ahead of their Carling Cup fourth-round tie against Bolton.
He had paid a second visit to his native Italy after the Blackburn win to spendtime with his father Giuseppe, 86, who is seriously ill.
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