Pathogenesis
Feline coronaviruses; (FCoV) are often divided into two groups:
- the highly pathogenic strains, feline infectious peritonitis viruses (FIP); 
- those strains which cause mild or no disease, the feline enteric coronaviruses (FECV)

1. Feline Enteric Coronavirus  (FECV)
•	Infects the apical columnar epithelium of intestinal villi of the duodenum, jejunum, and ileum. 
•	It is the most common type of Feline Coronavirus, but also the least pathogenic, and is often asymptomatic.  
•	In clinical cases it causes the tips of villi to slough, fuse with adjacent villi, and atrophy.
2. Feline Infectious Peritonitis (FIP)
•	Uncommon 
•	After ingestion or inhalation of virus, FIP initially replicates in tonsil or intestinal epithelium. 
•	Macrophage and monocyte associated viremia transports the virus to primary target organs such as liver, spleen, and  lymph nodes.
•	The clinical manifestation of the disease depends on the individual cats immune response. 
•	It can present as “Effusive FIP” or “Non Effusive FIP”
	a) Effusive FIP
•	Occurs with cats that exhibit a strong humoral response and low cell-mediated immunity
•	Persistent viremia
•	Systemic formation and deposition of immune complexes throughout the blood vessels and complement activation leads to vasculitis and vessel damage
•	Fluid and protein leaks into the body cavities
	b) Non Effusive FIP
•	Occurs in individuals with partial cell-mediated immunity and humoral immunity
•	Immune-mediated granulomatous lesions in abdominal viscera, lungs, eyes and brain.

	Carriers
•	Strong cell-mediated immune response with or without the presence of a humoral response
•	Either completely recover or become persistently infected asymptomatic carriers
•	Carriers will shed virus and may also develop FIP usually after periods of stress or a co-infection with Feline Leukemia Virus
•	Carriers can also completely recover and stop shedding virus at a later date.