Feline Calicivirus: Causes, Signs and How Vaccination Protects Your Cat

Feline calicivirus is one of the two core viruses behind what owners call cat flu, the other being feline herpesvirus. It spreads readily between cats through saliva, nasal discharge and shared spaces, surviving on bowls, bedding and human hands for days. Multi-cat homes, catteries and rescue environments see the fastest spread, which is why any new kitten should complete a vaccination course before meeting resident cats.

Signs vary with the strain. Most cats develop sneezing, clear to thick nasal discharge, eye watering and ulcers on the tongue, gums or nose that make eating painful, so drooling and refusal of food are common red flags. Some strains also produce transient lameness from joint inflammation, particularly in young kittens, while virulent systemic forms cause high fever, swelling of the face and limbs and severe illness across multiple organs. Healthy adult cats often show only mild sneezing and recover within a week or two, but kittens and immunocompromised cats can deteriorate quickly.

Treatment is supportive because antibiotics do not touch the virus itself. We focus on keeping cats eating: strong-smelling soft foods warmed slightly, appetite stimulants when needed and fluids for dehydration. Ulcerated mouths benefit from pain relief, and secondary bacterial infections are treated as they appear. Isolation at home during shedding prevents spread to other cats, and owners should wash hands and avoid sharing bowls between healthy and sick animals.

Prevention rests on the core feline vaccination schedule, which includes calicivirus protection starting during kittenhood with boosters through adulthood. No vaccine prevents infection outright because many strains circulate, but vaccinated cats develop far milder disease and shed less virus, protecting the wider cat community. Keep food bowls clean, quarantine newcomers until their course completes, and call us promptly if your cat sneezes persistently or you spot mouth ulcers; early supportive care shortens recovery dramatically.