Causes of FCV
There are numerous strains of feline calicivirus, and different strains cause different symptoms (e.g., one particular strain can cause ulcers on the paws as well as in the mouth).
Calicivirus usually affects the throat, and sometimes the lungs; the virus can also infect the intestines and has been isolated from feces. Calicivirus often occurs with another upper respiratory infection, such as feline herpes virus (FHV), rhinotracheitis virus, or chlamydiosis.
Calicivirus is spread through direct contact with the saliva, eye and nose discharges, and sometimes the feces, of an infected cat.
FCV is resistant to many disinfectants and can survive outside the cat's body for as long as 8 to 10 days, so it may be present in dishes, litter trays, and clothing, even after a thorough cleaning.
Many cats remain contagious for years, even though they may not show signs of disease. Healthy (i.e., asymptomatic), contagious cats are known as latent carriers.
Calicivirus is very common in kittens, multicat households, and pet adoption shelters. Outbreaks can occur in overcrowded, poorly ventilated, or unsanitary conditions; and where the cats are poorly fed, or stressed, either physically (e.g., extreme temperatures) or psychologically (e.g., introduction of a new cat).