This may be a serious situation. I hope all goes well for your cat. I'm sorry this happened.
I have had two different vets recommend spleen supplements for my cats when they had viral/bacterial stuff. It supports the immune system. In one case a round of Antibiotics only temporarily stopped the problem but afterwards two weeks or so of spleen supplementation solved it.
Two brands that I have used as per my holistic vets were: Standard process dessicated spleen. Some cats will eat this like a treat. Oh I don't have the other brand.
I had my cat have some symptoms and went to the weekend pet emergency place. After 1000 dollars she was still sick, partly from the immense stress of being in a mixed population hospital for 48 hours. I took her to a holistic vet who put her on the spleen supplement and she was better. Be careful who you take him/her to. You might feed him /her canned food for a bit, it has more liquid in it and a dehydrated cat won't pee, and will get sicker. I did this when my cat wasn't eating/drinking much. At least what she did eat was very moist and she did a bit better. Its not all that healthy, but if they need liquids this will help. Look for a holistic vet. You may have to drive but it may end up being quite a bit cheaper/faster/better. My holistic vet also worked at the er vet office, she just uses different approaches to fit different offices.
I just hate it when they are sick. I feel your pain. Hope you find a good vet fast/ the symptoms leave. Lay on hands and pray. Stay in faith- fear thoughts counteract prayer. If symptoms don't stop ask god to give you more of him, and try to visualize God loving you completely. I know how stressful this is and I pray for you and your pet. Grace