In early 2023, veterinarians on the island of Cyprus noted an upsurge in severe feline infectious peritonitis (FIP) caused by a coronavirus usually with relatively low pathogenicity.  It is estimated that 10,000 family-owned cats died as a result of the infection although the actual number may be far in excess of this figure given the large number of feral cats on Cyprus.  Studies showed that the virus responsible, termed FCoV-23, contained RNA from a canine coronavirus strain pCCoV.  A publication on the characterization of the recombinant virus* demonstrated deletion of several amino acids and changes in the spike protein modifying receptor binding and cell tropism.  Direct cat-to-cat transmission occurred based on epidemiologic evidence and supported by almost identical sequences among the recombinant feline virus isolates from affected cats.

This outbreak demonstrates the ability of coronaviruses to undergo both mutation and recombinant events with the possibility of new viruses emerging from interaction between animals and even with humans.  To date, there is no indication that either the canine coronavirus pCCoV or the feline virus F-CoV-23 is transmissible to humans that may be infected with specific strains including hCoV-229E or COVID caused by SARS-CoV-2.

*Attipa, C. et al., Emergence and Spread of Feline Infectious Peritonitis Due to a Highly Pathogenic Canine/Feline Recombinant Coronavirus. bioRxiv.2023 doi.org. /10.1101/2023.11.08.566182