"There has been speculation in the national media following confirmation of sickness within the camp, but we can reassure all supporters that the tie will go ahead as planned," Blackburn club secretary Andrew Pincher said.
Sam Allardyce's side were without Christopher Samba and David Dunn for the 5-0 defeat to Chelsea at Stamford Bridge on Saturday, due to what the manager has described as a virus. But it has not been confirmed if they are the two who have been diagnosed with swine flu.
"Dunny and Chris Samba have a virus," Allardyce said. "And a couple of the other lads who were playing against Chelsea have that virus or we think they are coming down with it.
"We will hopefully get them back next week when we have to go to Old Trafford. But it is one of those viruses that can see you out for up to six days so we'll have to see."
Midfielder Vince Grella has also been missing since suffering a thigh injury away with Australia on international duty, but Allardyce is hopeful he will be back for tomorrow's match.