Feline Calicivirus in Cats: Symptoms, Spread & Vet Signs
Feline calicivirus (FCV) is a common, highly contagious virus that causes cat flu, painful mouth ulcers, and eye and nose discharge in cats across the UK. Most cats recover with supportive care, but you should contact your veterinarian promptly if your cat stops eating, struggles to breathe, drools heavily, or develops a high fever. Below is a plain-language guide to what FCV looks like, how it moves between cats, and the specific warning signs that mean it is time to book a vet visit.
A cat resting comfortably at home.
What is feline calicivirus in cats?
Feline calicivirus (FCV) is a highly contagious virus and one of the leading causes of upper respiratory infection, often grouped with feline herpesvirus under the everyday term "cat flu". It is best known for causing painful ulcers on the tongue and gums, along with sneezing and eye and nose discharge.
FCV is widespread in the UK, especially where cats live in groups such as rescue centres, catteries, and multi-cat homes. The virus is hardy and can survive on surfaces, bowls, bedding, and hands for days, which is why it spreads so easily.
Many cats that recover from FCV become carriers and continue to shed the virus for weeks, months, or in some cases much longer. This carrier state is one reason the virus stays so common in the general cat population.
What are the symptoms of feline calicivirus in cats?
The most recognisable symptoms of feline calicivirus (FCV) in cats are mouth and tongue ulcers, drooling, sneezing, and eye and nose discharge. Signs usually appear within 2 to 10 days of exposure and range from mild to severe depending on the cat and the strain involved.
Common feline calicivirus symptoms UK owners tend to notice include:
Ulcers on the tongue, gums, lips, or hard palate
Drooling or reluctance to eat because the mouth is sore
Sneezing and clear or coloured nasal discharge
Watery or discharging eyes and conjunctivitis
Mild fever, low energy, and reduced appetite
Gingivitis and long-term mouth inflammation (stomatitis) in some cats
Oral disease and stomatitis
Oral ulcers and severe gum inflammation are a hallmark of FCV. Some cats develop chronic stomatitis and gingivitis, a painful, ongoing inflammation of the mouth that can make eating difficult and needs specific veterinary management.
Limping syndrome
Feline calicivirus can cause a temporary "limping syndrome" in cats, particularly kittens, where a fever and shifting lameness affect the joints. This is usually short-lived and often resolves as the cat recovers.
Virulent systemic FCV
A rare but serious form called virulent systemic feline calicivirus (VS-FCV) can cause high fever, swelling of the face and limbs, ulcers on the skin, and organ involvement. This form is uncommon, but it is a medical emergency and needs immediate veterinary attention.
How does feline calicivirus spread between cats?
Feline calicivirus spreads mainly through direct contact with an infected cat's saliva and nasal and eye secretions, and through contaminated objects such as bowls, bedding, litter trays, and human hands. Sneezing releases infectious droplets, and the virus can survive in the environment for days, so cats do not need to meet face to face to become infected.
The main routes of spread for FCV are:
Direct cat-to-cat contact, including grooming, sharing bowls, and close resting.
Airborne droplets from sneezing at short range.
Contaminated surfaces and equipment (fomites), including carriers and toys.
Human hands and clothing that carry the virus between cats.
Carrier cats that appear healthy but continue to shed the virus.
Because of these routes, FCV is a particular concern in multi-cat households, shelters, and catteries. Good hygiene, separate bowls, and isolating unwell cats all help reduce transmission. If you keep several cats and want to understand the wider risk picture, our overview of whether feline calicivirus is dangerous in cats puts the threat into context.
Is feline calicivirus the same as feline herpesvirus?
No. Feline calicivirus (FCV) and feline herpesvirus (FHV-1) are two different viruses, even though both cause cat flu and can look similar at first. FCV is more strongly linked to mouth and tongue ulcers, while FHV-1 tends to cause heavier eye involvement, including conjunctivitis and corneal ulcers.
Knowing the difference matters because the antiviral options a veterinarian may consider are not the same.
Feature | Feline calicivirus (FCV) | Feline herpesvirus (FHV-1) |
Typical signs | Mouth and tongue ulcers, drooling, mild eye and nose discharge, sometimes limping | Sneezing, heavier eye and nose discharge, conjunctivitis, corneal ulcers |
Course | Lifelong carrier state possible, some cats shed continuously | Lifelong infection, flare-ups often triggered by stress |
Antiviral a vet may use | EIDD-1931 (the CaliciX line) | Famciclovir (HerpX) |
Your veterinarian can confirm which virus is involved and tailor care accordingly. Both are managed rather than eliminated, since carrier cats can carry the virus long term.
When should UK cat owners see a vet about calicivirus?
You should see your veterinarian if your cat stops eating for more than a day, drools heavily, has visible mouth ulcers, struggles to breathe, or develops a high fever or facial swelling. Kittens, elderly cats, and cats with other health conditions should be seen sooner, because they can deteriorate quickly.
Book an urgent appointment if you notice any of these red flags:
Refusing food or water because of a sore mouth
Laboured or open-mouth breathing
Green or yellow discharge from the eyes or nose that is worsening
Swelling of the face, legs, or paws, or ulcers on the skin
Marked lethargy, collapse, or a cat that is hiding and unresponsive
Early veterinary input helps keep a mild case from becoming a serious one, especially in young kittens. It is also worth remembering that not every unwell cat has cat flu. Some serious feline illnesses share vague early signs, which is why our guide to the early warning symptoms of Feline Infectious Peritonitis (FIP) can help you tell one problem from another and get the right diagnosis faster.
How is feline calicivirus treated in cats?
There is no treatment that removes feline calicivirus (FCV) from the body, so care focuses on supporting the cat through the illness, controlling pain, keeping them eating, and treating any secondary bacterial infection. Most cats recover with good nursing, and your veterinarian will decide whether antiviral support is appropriate for the individual cat.
Supportive care commonly includes:
Keeping the nose and eyes clean and encouraging fluid intake.
Offering soft, warmed, strong-smelling food to tempt a sore mouth.
Pain relief and, where needed, antibiotics for secondary bacterial infection (antibiotics do not treat the virus itself).
Managing chronic stomatitis and gingivitis with a dedicated dental and medical plan.
For oral FCV disease such as stomatitis and gingivitis, the antiviral EIDD-1931 is one option a veterinarian may consider, and the CaliciX line is the FCV-positioned EIDD-1931 product. The figures below come directly from our catalogue, and any decision to use them must be made with your veterinarian.
Product | Active ingredient | Catalogue dosing | Notes |
EIDD-1931 Oral Capsules (€69.00) | EIDD-1931 | 1 capsule (15 mg) per 2.5 kg body weight, every 12 hours; 60 capsules per bottle; standard 60 days | The CaliciX line is the FCV-positioned EIDD-1931 product. Not for ocular or neurological cases, or cats not eating or defecating. EIDD-1931 is teratogenic, so it is not for pregnant or lactating queens. |
EIDD-1931 is the same nucleoside analogue used alongside GS-441524 in modern FIP care, where GS-441524 is the antiviral at the core of treatment. If you are researching that combined approach for a different diagnosis, our article on dual nucleoside analogue therapy for FIP explains the rationale in detail. FCV and FIP are separate conditions, so always confirm the diagnosis with your veterinarian before starting any medication.
Can feline calicivirus be prevented in cats?
Vaccination is the main way to reduce the risk and severity of feline calicivirus (FCV), and it is part of the core vaccine schedule most UK veterinarians recommend for kittens and adult cats. Vaccination does not guarantee that a cat will never catch FCV, because several strains circulate, but it helps lower the chance of severe disease.
Alongside vaccination, sensible hygiene makes a real difference:
Isolate new or unwell cats before introducing them to resident cats.
Use separate bowls, litter trays, and bedding for a poorly cat.
Wash hands and clean surfaces between handling different cats.
Reduce stress and overcrowding, which help viruses spread.
CureFIP is best known as a GS-441524 specialist that has supported the care of more than 100,000 cats since 2019, and that same commitment to clear, evidence-led information guides how we write about FCV. For UK readers who also want to understand how serious feline viral disease is managed across the region, our guide to FIP treatment in Europe offers useful background, while keeping FCV and FIP as the distinct conditions they are.
Frequently asked questions about feline calicivirus in cats
Is feline calicivirus in cats contagious to humans?
Feline calicivirus (FCV) is a cat-specific virus and is not considered a general health risk to people. It spreads readily between cats, however, so wash your hands and change clothing after handling an infected cat to avoid carrying the virus to other cats.
How long does feline calicivirus last in cats?
Most cats with feline calicivirus (FCV) show acute signs for around 1 to 3 weeks with supportive care. Some cats become carriers and continue to shed the virus for weeks or months afterwards, and a smaller number carry it long term.
Can a cat get feline calicivirus more than once?
Yes. Because several strains of feline calicivirus (FCV) circulate and immunity is not complete, a cat can be infected more than once. Vaccination and good hygiene help reduce both the risk and the severity of repeat episodes.
Does my cat need antibiotics for feline calicivirus?
Antibiotics do not treat the feline calicivirus (FCV) itself, because it is a virus, not a bacterium. Your veterinarian may prescribe antibiotics only if a secondary bacterial infection develops, so the decision should always be theirs.
What is the difference between calici in cats and FIP?
Calici in cats (FCV) is an upper respiratory and oral virus that causes cat flu and mouth ulcers, while Feline Infectious Peritonitis (FIP) is a separate, far more serious disease caused by a coronavirus. They need different diagnostics and treatments, so a veterinary diagnosis is essential before any medication is started.
If your cat is showing signs of cat flu, the best next step is a conversation with your own veterinarian about diagnosis and supportive care. To learn more about treatment options and to talk with our team, you are always welcome to explore the resources at CureFIP. We are here to help you understand the evidence, while every medical decision stays with you and your vet.
Thanks for the clear guide on feline calicivirus—really helpful to know the symptoms and when to call the vet. Speaking of helpful tools, I often use Free Analog Clock Online when I need a quick visual for timing my cat's medication schedule.
The part about cats becoming carriers after recovery surprised me—I didn’t realize they could keep spreading it for months. The mouth ulcers sound really painful, so I’ll watch for drooling more carefully now. I found Meowdoku helpful when comparing these symptoms to what my own cat showed last week.
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