Is it really a cat virus?

three days ago i saw my cat paws and mouth with blood, opened her mouth and realized had like a big cut on the side of her tongue but coming from inside out.  Took her to the vet and she said it is a virus.  Prescriped antibiotic and oxygenated water to rinse her mouth.  My cat cannot  eat or drink water, but the worse part is that she keeps putting her paws inside the mouth and keeps hurting herself more.  Do not know what to do, she is not playing or moving much.  Is there a virus of this nature? 

Thank you for the time.