Research overview: clinical stages of natural FIV progression

Like HIV, FIV infection progresses through recognizable phases: an acute stage with fever, lymphadenopathy, and transient neutropenia; a long, clinically silent asymptomatic stage that can last years; and a terminal stage marked by immunodeficiency, chronic infections, gingivostomatitis, weight loss, and sometimes neoplasia. Researchers have characterized progressive CD4+ T-cell decline and inverted CD4:CD8 ratios as immunologic hallmarks. Many cats live long, healthy lives, complicating prognosis. This overview synthesizes the clinical staging literature instead of a single paper, explaining how viral load and immune status track disease, why many infected cats die of unrelated causes, and why modern guidelines emphasize that an FIV-positive diagnosis is not an automatic reason for euthanasia.