Feline coronavirus is ubiquitous in cats but causes FIP only through mutation in a minority of infected animals, with the understanding of this relationship informing both prevention and welfare management.
FCoV-FIP welfare involves two distinct stages: the usually asymptomatic FCoV carrier state (no welfare impact) and the FIP disease state (severe, rapidly fatal before antiviral availability, still serious but now treatable). Prevention focuses on reducing FCoV exposure in multi-cat households through hygiene and density management. Once FIP develops, welfare management depends on accessing effective antiviral treatment. The transformation from universally fatal to largely treatable is one of veterinary medicine's recent welfare success stories, but access inequities mean that geography, income, and regulatory status affect whether cats receive life-saving treatment. Advocating for accessible, regulated antiviral access is a concrete welfare action.