There are several strains of feline calicivirus, which all have an affinity for the oral epithelium, and deep tissues of the lung. The virus ranges widely in virulence, some are non-pathogenic or cause mild disease, with salivation and ulceration of the oral mucosa and tongue, and others cause interstitial pneumonia and pulmonary edema. Two newly identified strains cause febrile limping syndrome, a transient self-resolving disease. Unlike FRV, FCV may persist in the environment for 8-10 days because it is relatively resistant to heat and detergent based disinfectants. FCV, however is susceptible to destruction by acidic solutions.
Aerosol transmission can occur via aerosol droplets, but is less likely.
Kittens can not get infected in utero, but the queen can still be a source of transmission when maternal antibody protection wanes. Kittens age 6-12 weeks are most susceptible. These carriers have persistently high antibody titers, but usually no clinical signs of illness. Calicivirus is shed continuously in saliva, feces, urine and foamites while FVR is shed intermittently, especially during times of stress, at which time they may also display clinical signs. These carriers are the main source of virus for susceptible cats.