Feline Calicivirus in Cats: Symptoms, Spread & UK Guide

Feline calicivirus (FCV) is a highly contagious virus that causes upper respiratory illness and painful mouth ulcers in cats, and it is one of the main causes of what UK owners call cat flu. The most common signs are sneezing, eye and nasal discharge, drooling, and sores on the tongue or gums. If you notice these signs, book a veterinary appointment promptly, because early assessment protects your cat's comfort and limits spread to other cats in the home.

A cat resting comfortably at home.

What is feline calicivirus in cats?

Feline calicivirus in cats is a common, highly contagious viral infection that mainly affects the upper respiratory tract and the mouth. It is one of the leading causes of feline upper respiratory disease worldwide, alongside feline herpesvirus.

FCV is not the same virus as feline herpesvirus (FHV-1), even though both are often grouped under the term cat flu. They are different viruses, they behave differently, and they can call for different management, so an accurate diagnosis from your veterinarian matters.

Many cats carry FCV without dramatic illness, while others develop clear respiratory and oral disease. Some infected cats become long-term carriers and continue to shed the virus for weeks or months, which is one reason FCV moves so easily through multi-cat homes, shelters, and catteries.

What are the symptoms of FCV in cats?

The most typical symptoms of FCV in cats are mouth ulcers, drooling, sneezing, nasal and eye discharge, fever, and reduced appetite. The mouth sores are often the most distinctive feature and a common reason UK owners first seek help.

Signs can range from mild to severe and may come and go, particularly in cats that carry the virus long-term. Below are the main patterns to watch for.

Mouth ulcers and cat mouth sores

Mouth ulcers are a hallmark of FCV. They commonly appear on the tongue, gums, and hard palate, and they can be genuinely painful.

Because the sores hurt, affected cats often drool, paw at the mouth, drop food, or stop eating altogether. Persistent oral inflammation is also linked with stomatitis, and you can read more about how the two connect in this overview of stomatitis in cats and its link to feline calicivirus.

Upper respiratory signs

Respiratory signs are the other core feature of FCV. Expect sneezing, clear or coloured nasal discharge, watery or discharging eyes, conjunctivitis, and sometimes a mild fever.

These signs overlap heavily with other causes of cat flu, which is exactly why a veterinary examination is important rather than guesswork at home. Secondary bacterial infections can develop on top of the virus and may need separate treatment.

Limping syndrome

Some strains of FCV cause a temporary lameness known as limping syndrome, where the cat develops fever and shifting joint pain. This is seen most often in kittens and young cats.

The limping usually settles, but it can be alarming to see. If you notice drooling, mouth sores, and lameness together, this combination is described further in this guide to feline calicivirus symptoms such as drooling, limping, and mouth sores.

Chronic and severe forms

A smaller number of cats develop chronic oral disease, with long-standing gingivitis and stomatitis that keeps the mouth sore and inflamed. These cats may struggle to eat and can lose condition over time.

Very rarely, a severe form called virulent systemic FCV can occur, causing high fever, swelling, and organ involvement. This form is uncommon but serious, and it needs urgent veterinary care.

How does calicivirus spread between cats?

FCV spreads mainly through direct contact with an infected cat's saliva and eye or nasal secretions, and through contaminated objects in the environment. Sneezing, shared food and water bowls, litter trays, bedding, grooming, and even human hands and clothing can all move the virus between cats.

The virus is hardy and can survive in the environment for up to around a month, and it resists many ordinary household disinfectants. This is why thorough cleaning and isolation of new or sick cats matter so much.

Carrier cats are a key part of the picture. A cat that appears healthy may still shed FCV and infect others, especially during periods of stress, which helps explain outbreaks in shelters, breeding groups, and multi-cat households.

To reduce spread in your home:

• Isolate any cat showing signs until your veterinarian advises otherwise.

• Use separate bowls, litter trays, and bedding for the affected cat.

• Wash your hands and change or clean clothing after handling a sick cat.

• Clean and disinfect surfaces with a product your veterinarian confirms is effective against calicivirus.

• Introduce new cats carefully and keep vaccinations up to date.

What should UK owners do if they suspect FCV?

If you suspect FCV, contact your veterinarian and book an examination, especially if your cat has mouth sores, is drooling, is not eating, or is struggling to breathe. Prompt assessment protects your cat's welfare and helps prevent spread to other cats.

Your veterinarian will usually diagnose FCV based on clinical signs and history, and may recommend further testing in complex or severe cases. There is no home test that can replace a professional diagnosis.

Seek same-day veterinary advice if your cat:

1. Stops eating or drinking for more than a day.

2. Shows laboured or open-mouth breathing.

3. Has severe mouth pain, heavy drooling, or cannot swallow.

4. Becomes very lethargic, collapses, or develops swelling and high fever.

For a fuller picture of the signs UK owners should track and when to escalate, this companion article on feline calicivirus signs, spread, and why it matters is a useful next read.

How is FCV in cats treated?

FCV treatment focuses on supportive care to keep the cat comfortable, hydrated, and eating, while the immune system responds, and your veterinarian directs the plan. Supportive measures often include pain relief, fluids, nutritional support, and treatment of any secondary bacterial infection.

Antibiotics do not act on the virus itself. They are used only when a secondary bacterial infection is present, so they are one part of a broader plan rather than a treatment for FCV directly.

For oral FCV disease, including stomatitis and gingivitis, the antiviral EIDD-1931 is used, and within the CureFIP range the FCV-positioned line is CaliciX and CaliciX Max, based on EIDD-1931. Any decision to use it, and the exact plan for your individual cat, must be made with your veterinarian.

The table below shows the EIDD-1931 Oral Capsules details exactly as listed in the CureFIP catalogue. Do not treat this as a personal prescription, always confirm suitability and dosing with your veterinarian.

Detail	EIDD-1931 Oral Capsules
Price	€69.00
Dose	1 capsule (15 mg) per 2.5 kg body weight, every 12 hours
Pack	60 capsules per bottle
Standard duration	60 days
Not suitable for	ocular or neurological cases, cats not eating or defecating, and pregnant or lactating queens

EIDD-1931 is teratogenic, which means it must never be used in pregnant or lactating queens. Because chronic oral cases can be complex, it also helps to understand why the mouth becomes so sore, which is explained well in this article on stomatitis in cats and why the mouth hurts so much.

Can feline calicivirus be prevented?

Vaccination is the main tool for reducing the impact of FCV, and it is part of the standard core vaccine schedule for cats in the UK. Vaccination does not always prevent infection completely, but it reduces the severity of disease and is strongly recommended by veterinarians.

Good hygiene and sensible management fill the gap that vaccination alone cannot cover. Keeping bowls, bedding, and litter trays clean, isolating sick cats, and being careful when introducing new cats all lower the risk of spread.

CureFIP is a specialist antiviral provider, and the wider network has supported more than 100,000 cats since 2019 across its treatment areas. If you are weighing up options for oral FCV disease, your veterinarian remains the right person to confirm the diagnosis and the plan.

Frequently Asked Questions

Is feline calicivirus in cats contagious to humans?

No, feline calicivirus does not infect humans. It spreads between cats through saliva, secretions, and contaminated objects, so you can still carry the virus on your hands or clothing and pass it to other cats even though you cannot catch it yourself.

How long does FCV last in cats?

Many cats recover from an acute FCV episode within one to two weeks with supportive care, but some become long-term carriers and shed the virus for months. Cats with chronic oral disease can have ongoing or recurring signs, so follow your veterinarian's monitoring advice.

What is the difference between FCV and feline herpesvirus?

FCV and feline herpesvirus (FHV-1) are two different viruses that both cause cat flu, but FCV is especially associated with mouth ulcers and oral disease. Your veterinarian can distinguish them and tailor management accordingly, since the products and approach can differ.

Can my other cats catch calicivirus from an infected cat?

Yes, FCV spreads readily between cats, particularly in multi-cat homes. Isolate the affected cat, use separate bowls and litter trays, wash your hands after handling, and keep vaccinations current to reduce the risk to your other cats.

When should I take my cat to the vet for FCV symptoms?

See your veterinarian promptly if your cat has mouth sores, heavy drooling, is not eating, or has breathing difficulty. Same-day advice is important if your cat collapses, develops a high fever with swelling, or cannot swallow.

If your cat is showing signs of feline calicivirus, the kindest next step is a conversation with people who understand it. Learn more about the available oral FCV options and talk with our team or your own veterinarian by visiting the CureFIP website, where you can explore support tailored to your cat and get a professional plan in place.