My Bengal cat had a fever and lethargy for several days. When will he return to normal?

My bengal cat, Conan, had a fever for several days. We took him to the ER and the vet for blood work, ex rays, etc. The blood work was clear, as well as the ex-rays. He had a rabies/distemper vaccination a week before he started becoming lethargic. It was also discovered that he had a minor UTI, which the vet prescribed an antibiotic. He has been on it for 5 days and his fever has finally subsided. He is still sleeping a lot and doesn't seem like himself before this all started. Will he ever return to normal?