steroids will definitely raise your BG...since its a pack Im assuming you'll only be on it a few days though right?
I wouldnt "not take" the meds as they will definitely help with the upper respitatory issues you are having - steroids do amazing things eventhough they much our BG's like crazy. lol
Personally, I'd just watch my BG's a little closer - if you are on insulin be prepared to need a little bit more.
I'm on a low dose of prednisone every day because of my Stills Disease and its does considerable things to my BG's but I'm on it constantly so my insulin rates work with the meds but in your case it will only be a few days, so Id do damage control with the BG's so you can get the upper respiratory infection outta there and you can get back to normal