A fatal disease of both domestic and exotic cats (particularly cheetahs) caused by feline infectious peritonitis virus, a member of the Coronaviridae family. There are multiple strains of the virus which vary in virulence. Feline infectious peritonitis virus is closely related morphologically, genetically, and antigenically to other members of the Coronaviridae and arises as mutants from feline enteric coronaviruses, which infect cats but generally induce very mild or inapparent gastroenteritis. All coronaviruses are single-stranded ribonucleic acid (RNA) viruses with poor or no error correction during replication, resulting in relatively high mutation rates.