Over the weekend, Louisa revealed she had been unwell, after Simon Cowell criticised her first performance of Justin Bieber's 'Love Yourself'. He described the performance as "tense", with Louise later admitting she had been on voice rest, after not being able to speak or sing.
Now, reports suggest Louisa's illness could force her to miss out on Saturday night's semi-finals show, with fears she could pass on her symptoms to the other contestants.
A show insider told The Daily Star: "We're worried she could be too ill to continue next week. We couldn't give her a free pass to the final, there would be uproar. But if any of the other contestants come down with the same thing we will really struggle."
"Olly is also sick and struggling," they added. "The bugs going round at the moment are really nasty."
Louisa is set to go head-to-head with Lauren Murray, Che Chesterman and Reggie 'N Bollie for a spot in this year's X Factor final, after 4th Impact were eliminated from the show during last night's live results show.
The girl group faced Lauren in the sing-off, but were later sent home after the judges' votes went to deadlock and Caroline Flack revealed 4th Impact had received the fewest public votes.
Just as the show cut off air, it was revealed Celina had collapsed on stage and had to be treated by paramedics.
Reassuring everyone that she was ok, Cheryl Fernandez-Versini shared an update with fans on The Xtra Factor.
She said: "I could see her, I was talking to her and she wasn't engaging so I brought her closer to me to ask if she's okay and she just went, she passed out. She is fine though, she is with her family and her mum is here. She's fine, I promise you, she's been sorted out right now."
The X Factor continues Saturday and Sunday 5-6 December on ITV.
For exclusive competitions and amazing prizes visit Reveal's Facebook page NOW!