On Monday, Sam Allardyce confirmed that three unnamed members of his squad had come down with swine flu and that it had been within the camp for a number of days.
But there was little evidence of any ill effects amongst those playing in Tuesday's match - including suspected victim David Dunn, who came off the substitutes' bench - and afterwards assistant manager Neil McDonald said there were no new cases to report of players having fallen sick.
"It's under control. We had a squad up on Monday and everyone came through from that squad which was great," McDonald said.
"We will monitor it on a 24-hour basis. Everyone seems okay."
The Health Protection Agency has warned players that spitting on the pitch could increase the risk of passing on infection during matches and McDonald said that the club was doing everything in its power to ensure the virus did not spread.
"I'm not a medic so I don't know how it is passed on, but you can spit, cough, sneeze - anything that comes out of your body is how it is passed on I suppose," he said.
"I think there is always a problem in it spreading, but we are doing our best to try and contain everything by doing the right things and monitoring everyone, and we will continue to do that.
"Hopefully it won't spread any more, fingers crossed."
McDonald later confirmed boss Allardyce decided to keep away from his players on Tuesday.
Allardyce spent the whole of the match in the Ewood Park stands rather than on the touchlines because he was feeling unwell.
"Sam is feeling a little unwell, so he sat upstairs as he wanted to see the picture from above," said McDonald.
"He trusts in his staff which is excellent, and he was at the game but he didn't want to take any chances.
"He shot out just to make sure nobody gets what he might have."
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