Feline infectious peritonitis is a fatal inflammatory disease caused by a mutated feline coronavirus, but antiviral treatments have transformed it from certain death to curable in most cats.
FIP has historically been one of the most distressing diagnoses in feline medicine because of its rapid progression and complete lack of treatment options. Affected cats deteriorate from apparent health to severe illness within days, with fluid accumulation causing breathlessness, lethargy, and appetite loss. The transformation in prognosis from GS-441524 antivirals represents a genuine welfare revolution — cats that would have died within days achieve full clinical remission and return to normal quality of life. However, treatment access is complicated: GS-441524 was not initially licensed in many countries, forcing owners to navigate black-market sources or import medications. Licensed products are now available in several countries, improving access. Treatment monitoring requires frequent blood tests and clinical assessments, and the 12-week minimum course demands sustained owner commitment. Relapse after premature treatment cessation requires repeat courses. Full monitoring throughout treatment is essential.