[2] Different strains of FCV can vary in virulence (the degree of pathogenicity within a group or species of microorganisms or viruses as indicated by case fatality rates and/or the ability of the organism to invade the tissues of the host).

The disease is caused by direct viral invasion of epithelium and endothelium and secondary host immune response.

In private households, FCV is present in about 10% of cats (either in active or carrier state), while the prevalence in shelters or catteries is 25 to 40%.

Acute signs of FCV include fever, conjunctivitis, nasal discharge, sneezing, and ulceration of the mouth (stomatitis).

Stomatitis and polyarthritis can develop without any upper respiratory infection signs, but fever and loss of appetite may occur.

[7] Initial clinical signs include discharge from the eyes and nose, ulceration in the mouth, anorexia, and lethargy, and occur in the first one to five days.

[9] Later signs include fever, edema of the limbs and face, jaundice, and multiple organ dysfunction syndrome.

[10] Attenuated FCV vaccine has been shown to possibly cause mild upper respiratory infection.

[7] The only vaccine licensed for prevention of VS-FCV is CaliciVax, manufactured by Fort Dodge Animal Health, a division of Wyeth.

However, FCV is very contagious, and latently infected cats will continue to shed viruses, so complete control is difficult.

Quaternary ammonium compounds are not thought to be completely effective, but a 1:32 dilution of household bleach used with a detergent and sufficient contact time does seem to kill the virus.

[3] Herbal extracts as a source of compounds with an antiviral activity has attracted significant attention recently.

On the contrary, authors of the second article[14] claimed that kaempherol showed anti-FCV activity, but theaflavin treatment was insufficient.