Fever in cats can be caused by a variety of illnesses, including bacterial or viral infections, inflammation, autoimmune diseases, and certain types of cancer.
If your cat has a fever, it's important to consult a vet to determine the underlying cause. In some cases, a fever could be a symptom of serious conditions, such as Feline Leukemia. In some cases, fevers could be associated with viruses like the Feline Herpesvirus (FHV-1).