Research overview: regressive versus progressive FeLV infection

After exposure, cats follow divergent outcomes that modern molecular testing has clarified. In progressive infection, the immune system fails to contain the virus, leading to persistent viremia, ongoing shedding, and high risk of FeLV-related disease and death. In regressive infection, the cat mounts an effective response, clears detectable viremia, and harbors latent proviral DNA that PCR can detect but that usually does not cause clinical disease, though reactivation is possible. This overview gathers findings across the outcome-classification literature rather than one source, explaining how antibody, antigen, and PCR testing distinguish these states, why outcome depends on age and immune competence at exposure, and why the regressive category reshaped prognosis and testing interpretation for exposed cats.