It is a virus that affects the upper airways, is very contagious and is transmitted mostly by direct contact, although indirect contact is possible since the virus can persist in the environment for up to 1 month. The prevalence of FCV infection is much higher in feline colonies than in domestic cats.

Symptoms appear after a 2-10 day incubation and include sneezing, conjunctivitis, nasal and ocular discharge, loss of appetite, fever and apathy. Oral ulcers are often present, and lameness due to transient arthritis can sometimes be observed, especially in kittens. The infection can be overcome within 14-21 days with the possibility that the cat becomes a carrier and therefore eliminates the virus for life.

Recently, a high genetic instability of the virus has been highlighted, which shows rapid mutations with the onset of new strains responsible for a very serious systemic form, often lethal and fortunately infrequent. “Systemic virulent feline calicivirosis” can mainly affect vaccinated adult cats with a much more serious infection than the classic form with distinctive symptoms such as ulcerative dermatitis, skin edema on the head and limbs and high mortality.

Although the vaccine does not appear to protect against these different strains, vaccination is still recommended.