Is my bub's loss of appetite normal?

My 6 month old has been sick with a respiratory virus for around 9 days. It was a nasty one and she lost her appetite. She's usually a big eater - easily goes through 180mls x 5 formula a day plus solids. By about day 3 of her illness she stopped eating at much - she might get through 60 mls of her bottle, then I'll try and get her to have the rest and she might take another 20-40 mls. I backed of the solids to make sure she gets as much nutritional foods as possible. She's definitely on the mend, much happier, sleeping better, less congested but still her appetite hasn't improved. So yeah, is this normal and when should I expect it to improve?