Jen...I hope it builds up in his system soon! Any chance of steaming him or dabbing a TINY bit of Vicks under his nose?

I copied this from another post, and I am sure you and your vet thought of everything...but I just quote it here in case!

Then there is Chlamydia but that is WAY to expensive to test for.It cost us 900 bucks to find out my cat Trudy had it VERY bad.But she had wet coughs and laringitis and snotty nose.
HUGS and more prayers for Jasper!