By Dial A Vet Veterinary Team
Feline calicivirus (FCV) is one of the two viruses behind most cases of cat flu, and it is everywhere cats gather. What sets it apart is the mouth. Painful ulcers on the tongue, gums, or roof of the mouth can stop a cat eating within a day or two, and a cat that will not eat gets sick quickly. Most cats recover with good nursing and veterinary support. Kittens, unvaccinated cats, and cats in shelters or catteries are at higher risk of severe illness, and a rare aggressive strain can be life-threatening.
Key takeaways
- FCV causes sneezing, eye and nose discharge, fever, and often painful mouth ulcers.
- It spreads through saliva, eye and nose secretions, and contaminated bowls, bedding, hands, and clothing.
- Some recovered cats keep shedding the virus for months or longer without looking sick.
- Vaccination is part of the core F3 vaccine in Australia. It does not prevent every infection, but it greatly reduces severity.
- A cat that stops eating for 24 hours, struggles to breathe, or develops swelling of the face or paws needs prompt veterinary care.
Signs to watch for
- Sneezing and a runny nose
- Watery or red eyes
- Ulcers on the tongue, gums, lips, or nose
- Drooling, pawing at the mouth, or dropping food
- Reduced appetite or refusal to eat
- Fever, lethargy, and hiding
- Sudden limping or stiffness in kittens, sometimes moving from leg to leg (often called limping syndrome)
FCV is also linked to long-term mouth inflammation in some cats (chronic gingivostomatitis), which causes ongoing pain when eating.
How cats catch it
The virus passes directly between cats through sneezes, grooming, and shared food or water. It also survives on surfaces for days to weeks and can be carried on hands, clothes, and equipment. Multi-cat homes, shelters, breeders, and boarding catteries are where it spreads most easily. Carrier cats look healthy but intermittently shed virus, which is how infection keeps circulating. FCV does not infect people or dogs.
Virulent systemic calicivirus
A rare, highly aggressive form called virulent systemic feline calicivirus (VS-FCV) causes outbreaks rather than single cases, usually in shelters or clinics. Signs can include high fever, swelling of the face and legs, skin sores, yellowing of the gums or eyes, and severe illness, even in vaccinated adults. It is uncommon, but if several cats in a group become very sick quickly, contact a vet immediately.
When to see a vet
Go to an emergency vet now if your cat:
- Is breathing with effort or with its mouth open
- Is very weak, collapsed, or not drinking
- Has swelling of the face or paws with fever, or yellow gums
- Is a young kitten that is cold, flat, or not feeding
Book a same-day appointment if: your cat has not eaten for 24 hours, is drooling or has mouth ulcers, has thick yellow or green discharge, or is limping with a fever. Cats that go without food for more than a day or two risk serious liver problems.
Reasonable to monitor at home with a call to your clinic: an adult cat with mild sneezing that is still eating, drinking, and acting like itself. Book in if things are not improving within a few days.
How vets diagnose and treat FCV
Diagnosis is often made from the signs, especially when mouth ulcers are present. In shelters, catteries, or unusual cases, your vet may swab the mouth, eyes, or throat for PCR testing to confirm the virus and check for others such as feline herpesvirus. See also cat flu.
There is no medicine that kills the virus directly, so treatment supports the cat while its immune system clears the infection. Depending on severity, that can include pain relief for mouth ulcers, fluids for dehydration, appetite support, nebulisation to loosen congestion, and antibiotics if secondary bacterial infection is suspected. Some cats need a short hospital stay or a feeding tube until they can eat on their own. Your vet will choose treatment based on your cat's condition.
Nursing at home
- Offer soft, strong-smelling food, warmed slightly to body temperature. Smell drives appetite when a cat's nose is blocked.
- Gently wipe eye and nose discharge with a soft cloth dampened with warm water.
- Sitting with your cat in a steamy bathroom can ease congestion.
- Keep the sick cat separate from other cats, with its own bowls and litter tray.
- Wash your hands and change clothes after handling the sick cat.
- Do not give human cold or pain medicines. Paracetamol and many others are toxic to cats.
Prevention
- Keep core vaccinations current, including kitten boosters and adult boosters as your vet recommends.
- Isolate new cats for a period before introducing them to resident cats.
- Choose catteries that require vaccination and have good hygiene.
- FCV resists some common disinfectants. Ask your vet about products proven to work against it, such as properly diluted bleach on suitable surfaces.
FAQ
Can humans catch feline calicivirus?
No. FCV only infects cats. People can carry it between cats on hands and clothing, though.
My cat is vaccinated. How did it get calicivirus?
The vaccine reduces the severity of illness but cannot prevent every infection, partly because there are many strains. Vaccinated cats usually have milder disease.
How long does recovery take?
Many cats improve within one to three weeks. Ulcers and appetite usually recover together.
Will my cat always carry the virus?
Some recovered cats shed virus for weeks to months, and a smaller number for longer. Many eventually stop.
Talk with a vet
If your cat is sneezing, drooling, or off its food and you need help deciding how urgent it is, our vets can assess the situation by video. Book a consult at dialavet.com. Mouth ulcers, dehydration, and breathing problems often need hands-on care, so we will tell you when your cat should be seen in a clinic.
References
- Cornell Feline Health Center. Feline Calicivirus.
- Merck Veterinary Manual. Feline Respiratory Disease Complex.
- WSAVA Vaccination Guidelines for Dogs and Cats.
- International Cat Care. Cat flu information for owners.
Disclaimer: Educational only. This page does not replace an examination or advice from your own veterinarian. If your cat is struggling to breathe or has stopped drinking, contact a veterinary hospital immediately.
