Last updated: May 6, 2026

Feline Calicivirus: Symptoms, Treatment & Vaccination Guide

If your cat has ever developed a runny nose, started sneezing repeatedly, or suddenly refused to eat because of painful sores in the mouth, feline calicivirus may have been the cause. This virus is one of the most widespread infectious agents in the domestic cat population, and it is responsible for a significant percentage of upper respiratory infections seen in veterinary clinics and shelters around the world. Understanding feline calicivirus — how it spreads, what it does to the body, and how to prevent it — is essential knowledge for every cat owner, foster parent, and rescue volunteer.

What Is Feline Calicivirus?

Feline calicivirus is a small, non-enveloped RNA virus belonging to the family Caliciviridae. It is one of the two primary viral causes of upper respiratory infection in cats, the other being feline herpesvirus type 1 (FHV-1). While herpesvirus tends to cause more severe eye involvement, feline calicivirus is particularly associated with oral ulceration and, in some cases, a distinctive lameness known as limping syndrome.

One of the challenges with feline calicivirus is its genetic diversity. The virus mutates readily, which means there are many different strains circulating at any given time. This variability is why some cats experience only mild sniffles while others develop severe illness, and it is also why vaccination — though highly effective at reducing disease severity — does not always prevent infection entirely. The virus is remarkably hardy in the environment, capable of surviving on surfaces for up to a month under the right conditions, which makes it a persistent problem in multi-cat households, catteries, and animal shelters.

How Feline Calicivirus Spreads

Feline calicivirus is highly contagious and spreads through several routes. The most common is direct contact — nose-to-nose greetings, mutual grooming, sharing food bowls, and sneezing are all efficient ways for the virus to pass between cats. When an infected cat sneezes, tiny droplets containing viral particles can travel several feet through the air and land on nearby cats, surfaces, or human hands.

Indirect transmission is equally important. The virus can survive on food bowls, litter trays, bedding, cages, clothing, and human hands for days to weeks depending on temperature and humidity. A person who handles an infected cat and then touches a healthy cat without washing their hands can easily transfer the virus. This is why feline calicivirus outbreaks in shelters and veterinary clinics can be so difficult to contain — the virus does not need a living host to remain infectious.

Cats can begin shedding the virus before they show any symptoms, which means a seemingly healthy new arrival at a shelter or a foster home can introduce feline calicivirus to the entire population before anyone realizes there is a problem. Shedding typically begins two to three days after infection and can continue for two to three weeks during acute illness — and much longer in carrier cats.

Symptoms of Feline Calicivirus

The symptoms of feline calicivirus vary depending on the strain involved, the age and immune status of the cat, and whether the cat has been previously vaccinated. The incubation period is typically two to six days, after which signs can range from barely noticeable to severe.

Oral ulcers: This is the hallmark sign of feline calicivirus and the symptom most likely to distinguish it from feline herpesvirus. Painful ulcers develop on the tongue, hard palate, gums, lips, and sometimes the tip of the nose. These sores make eating and drinking extremely painful, and many cats will approach their food bowl, show interest, and then walk away because the act of chewing or swallowing hurts too much. Drooling is common. The ulcers typically begin as small blisters that rupture and leave raw, reddened craters.

Upper respiratory infection (URI): Sneezing, nasal discharge (clear to yellowish), nasal congestion, and conjunctivitis are all common. The cat may breathe through its mouth if nasal passages are severely blocked. Fever, lethargy, and loss of appetite accompany the respiratory signs. In kittens and debilitated cats, a secondary bacterial infection can develop on top of the viral infection, leading to pneumonia — a potentially life-threatening complication.

Limping syndrome (FCV-associated polyarthritis): Some strains of feline calicivirus cause an acute, transient lameness that can be alarming to owners. The cat may suddenly begin limping, favoring one or more legs, or refuse to walk altogether. The joints may appear swollen and painful to the touch. This limping syndrome is caused by inflammation of the joint lining and is most commonly seen in kittens, though adult cats can be affected. It sometimes occurs without any respiratory signs at all, which can make diagnosis confusing. The good news is that limping syndrome caused by feline calicivirus is almost always self-limiting and resolves within a few days to two weeks without lasting joint damage.

Chronic stomatitis: In some cats, feline calicivirus infection contributes to a chronic, painful inflammation of the mouth and gums known as feline chronic gingivostomatitis. This condition involves severe, persistent inflammation at the back of the mouth and can make eating permanently difficult. It is thought that an overactive immune response to the ongoing presence of the virus plays a role, and treatment often requires long-term management including dental extractions.

Virulent Systemic Feline Calicivirus (VS-FCV)

While most strains of feline calicivirus cause manageable upper respiratory illness, a rare and far more dangerous form exists: virulent systemic feline calicivirus, or VS-FCV. This highly pathogenic variant does not confine itself to the respiratory tract and mouth. Instead, it spreads throughout the body, attacking multiple organ systems simultaneously.

Cats infected with VS-FCV may develop high fever, severe facial and limb swelling (edema), skin ulceration — particularly on the ears, paw pads, and around the mouth — jaundice from liver involvement, and signs of disseminated intravascular coagulation (DIC), a catastrophic blood-clotting disorder. The mortality rate for virulent systemic feline calicivirus is alarmingly high, often reaching 50 to 60 percent even with intensive veterinary care, and in some outbreaks it has exceeded 80 percent.

VS-FCV outbreaks tend to occur in veterinary hospitals, shelters, and catteries where cats are housed in close proximity. Critically, even vaccinated cats can be affected, though vaccination may reduce the severity of disease. Outbreaks require immediate isolation of affected cats, aggressive disinfection, and strict biosecurity protocols to prevent further spread. Fortunately, VS-FCV outbreaks are uncommon, and the vast majority of feline calicivirus cases involve conventional, far less dangerous strains.

Diagnosis of Feline Calicivirus

In many cases, a veterinarian will diagnose feline calicivirus based on clinical signs alone — the combination of oral ulcers and upper respiratory symptoms in a cat is highly suggestive. However, because feline herpesvirus can cause similar respiratory signs and other conditions can cause oral ulcers, laboratory confirmation is sometimes pursued.

The most common diagnostic test is a polymerase chain reaction (PCR) test, which detects viral genetic material in swabs taken from the mouth, nose, or eyes. PCR is highly sensitive and can confirm the presence of feline calicivirus even in cats that are shedding small amounts of virus. Virus isolation — growing the virus from a sample in a laboratory — is another option, though it takes longer and is used less frequently in general practice. It is worth noting that a positive test in a cat without symptoms may simply indicate a carrier state rather than active disease.

Treatment for Feline Calicivirus

There is no antiviral drug that specifically eliminates feline calicivirus. Treatment is supportive, focused on keeping the cat comfortable, maintaining hydration and nutrition, and preventing or treating secondary bacterial infections while the immune system clears the virus.

Fluid therapy: Cats that have stopped eating and drinking due to mouth pain often become dehydrated. Subcutaneous or intravenous fluids may be necessary to restore and maintain hydration, especially in kittens and cats with prolonged illness.

Pain management: Oral ulcers are extremely painful. Your veterinarian may prescribe pain medications such as buprenorphine or meloxicam to help your cat feel comfortable enough to eat. Managing pain is not optional — it is a critical part of treatment because a cat that refuses food for several consecutive days can develop hepatic lipidosis (fatty liver disease), a serious secondary condition.

Nutritional support: Offering strong-smelling, soft, or warmed food can encourage eating. Cats with severe oral ulcers may tolerate pureed or liquid diets more easily. In some cases, appetite stimulants are prescribed. If a cat cannot eat on its own for more than three days, a feeding tube may be considered.

Antibiotics: While antibiotics do not treat the virus itself, they are frequently prescribed to combat secondary bacterial infections that develop when the virus damages the respiratory lining and oral tissues. Without antibiotic support, a straightforward viral URI can progress to bacterial pneumonia.

Nebulization and steam therapy: For cats with significant nasal congestion, placing them in a steamy bathroom or using a nebulizer can help loosen nasal secretions and make breathing easier.

The Carrier State

One of the most important aspects of feline calicivirus biology is the carrier state. After recovering from acute infection, a significant number of cats — estimates range from 10 to more than 50 percent — continue to harbor and shed the virus for weeks, months, or even years without showing any symptoms themselves. These carrier cats appear perfectly healthy but are a constant source of infection for other cats in the household or community.

The virus persists primarily in the tonsils and oral tissues of carrier cats. Shedding can be continuous or intermittent, and stress — such as rehoming, boarding, surgery, or the introduction of a new pet — can increase shedding levels. Some carriers eventually clear the virus on their own over a period of months to years, but others remain lifelong shedders. This is one reason why feline calicivirus is so difficult to eradicate from multi-cat environments: even if every sick cat recovers, asymptomatic carriers can restart the cycle of transmission at any time.

For adopters bringing a new cat home, this carrier state is worth understanding. A cat adopted from a shelter may carry feline calicivirus without any visible signs. Proper quarantine procedures, gradual introductions, and keeping all cats in the home up to date on vaccinations are the best ways to manage this risk. If you are considering adding a new cat to your family, browse the cats available on our adoption page and speak with the shelter team about each cat’s health history.

Vaccination — FVRCP

Vaccination is the cornerstone of feline calicivirus prevention. The calicivirus component is included in the FVRCP vaccine — a core vaccine that also protects against feline viral rhinotracheitis (herpesvirus) and feline panleukopenia (distemper). Every cat, regardless of whether it lives indoors or outdoors, should receive the FVRCP vaccine. It is considered a core vaccine by the American Association of Feline Practitioners (AAFP) and the World Small Animal Veterinary Association (WSAVA).

Kittens typically begin the FVRCP series at six to eight weeks of age, with booster doses given every three to four weeks until they are 16 to 20 weeks old. This series is essential because maternal antibodies — protective antibodies passed from the mother — wane at variable rates, and the series ensures the kitten is covered as maternal immunity fades. An additional booster is given one year after the initial series, followed by boosters every three years for the remainder of the cat’s life.

Because feline calicivirus mutates frequently and exists in many strains, no vaccine provides complete protection against every variant. However, vaccination significantly reduces the severity and duration of illness if a vaccinated cat does become infected. Vaccinated cats are less likely to develop severe oral ulcers, less likely to stop eating, less likely to require hospitalization, and far less likely to die from the infection. Vaccination also reduces the amount of virus a cat sheds, which helps protect other cats in the community. Many of the cat breeds in our directory are equally susceptible to feline calicivirus, making vaccination important regardless of breed.

Cleaning and Disinfection

Because feline calicivirus is a non-enveloped virus, it is more resistant to environmental conditions and many common disinfectants than enveloped viruses like feline herpesvirus. Standard household cleaners, including many quaternary ammonium compounds, are not reliably effective against calicivirus. The gold standard for disinfection is a dilute bleach solution — one part household bleach to 32 parts water (approximately half a cup per gallon). Surfaces must be cleaned of organic matter first, then the bleach solution should be applied and allowed to sit for a minimum of 10 minutes of contact time before rinsing.

Accelerated hydrogen peroxide products (such as Rescue/Accel) are also effective against calicivirus and are less corrosive than bleach, making them popular in veterinary clinics and shelters. Potassium peroxymonosulfate (such as Trifectant or Virkon) is another effective option.

In a household where a cat has been diagnosed with feline calicivirus, thorough disinfection of food bowls, water dishes, litter trays, bedding, toys, and any surfaces the cat has contacted is essential. Items that cannot be adequately disinfected — such as cardboard scratchers or fabric toys — should be discarded. Hands should be washed thoroughly with soap and water after handling an infected cat and before touching other cats. Clothing worn while caring for a sick cat should be changed before interacting with healthy cats.

Shelter Cats and Calicivirus

Animal shelters face a particular challenge with feline calicivirus. The combination of high population density, stress, cats of unknown vaccination history, and constant turnover creates ideal conditions for the virus to spread. Studies have found that up to 25 to 40 percent of cats in shelters may be actively shedding feline calicivirus at any given time, and outbreaks of upper respiratory infection are one of the most common health crises shelters deal with.

Well-managed shelters mitigate this risk through several strategies: vaccinating every cat on intake, housing cats individually rather than in communal rooms when possible, using effective disinfection protocols between occupants, minimizing the length of stay, providing stress-reduction measures such as hiding boxes and predictable routines, and implementing isolation areas for cats showing respiratory symptoms. Foster-based rescue programs, where cats are housed in private homes rather than a central facility, often see lower rates of calicivirus transmission simply because they eliminate the shelter environment entirely.

If you are adopting a cat from a shelter and notice mild sneezing or a small amount of nasal discharge, do not be alarmed — this is common and usually resolves within a week or two in the calm environment of a new home. However, always follow up with your own veterinarian within a few days of adoption to establish care and discuss any ongoing symptoms. Cats available for adoption through our rescue receive veterinary evaluation and vaccinations as part of the intake process.

Recovery Timeline

For the majority of cats with uncomplicated feline calicivirus, the recovery timeline follows a fairly predictable pattern. Symptoms typically appear two to six days after exposure. The acute phase of illness — fever, sneezing, nasal discharge, oral ulcers, and reduced appetite — usually lasts seven to 10 days. Oral ulcers generally begin to heal within one to two weeks, though larger or deeper ulcers may take slightly longer.

Most otherwise healthy adult cats are clinically recovered within two to three weeks. Kittens, elderly cats, and cats with other health conditions may take longer and are more likely to experience complications such as secondary bacterial pneumonia. Cats with limping syndrome typically see lameness resolve within 48 hours to two weeks. Throughout recovery, maintaining hydration, ensuring adequate caloric intake, and keeping the cat in a warm, stress-free environment are the most important things an owner can do.

After clinical recovery, remember that many cats enter a carrier state and continue shedding virus for an extended period. Your veterinarian can advise on how to manage this in a multi-cat household and when it may be safe to introduce recovered cats to other feline housemates.

Frequently Asked Questions

Can humans catch feline calicivirus from cats?

No. Feline calicivirus is species-specific and does not infect humans. You cannot catch a respiratory infection or develop mouth ulcers from caring for a cat with FCV. However, you can carry the virus on your hands, clothing, and shoes, so practicing good hygiene when handling an infected cat is important to prevent spreading the virus to other cats in your home or community.

Can an indoor-only cat get feline calicivirus?

Yes, though the risk is lower than for cats with outdoor access. The virus can be brought into the home on shoes, clothing, or hands — or introduced by a new cat that is an asymptomatic carrier. This is one of the reasons why the FVRCP vaccine is recommended as a core vaccine even for strictly indoor cats. Boarding, grooming appointments, and veterinary visits are other potential exposure points.

Is feline calicivirus the same as cat flu?

“Cat flu” is a colloquial term that typically refers to upper respiratory infections caused by either feline calicivirus or feline herpesvirus, or sometimes both at once. The two viruses are different organisms with different behaviors — herpesvirus tends to cause more severe eye disease and can reactivate from latency during stress, while feline calicivirus is more associated with oral ulcers and limping syndrome — but the term “cat flu” is commonly applied to both.

My cat was vaccinated but still got calicivirus. Does the vaccine not work?

The FVRCP vaccine is highly effective but does not guarantee complete immunity against every strain of feline calicivirus due to the virus’s genetic diversity. What vaccination does reliably accomplish is a significant reduction in disease severity. Vaccinated cats that do become infected typically experience milder symptoms, recover faster, shed less virus, and are far less likely to develop life-threatening complications compared to unvaccinated cats. Vaccination remains the single best protection available.

How long is a cat with calicivirus contagious?

A cat with acute feline calicivirus infection is contagious from approximately two to three days after exposure and remains contagious throughout the course of illness, typically two to three weeks. However, many cats become chronic carriers after recovery and can shed the virus intermittently for months or years. During the acute illness, strict isolation from other cats and thorough disinfection practices are essential to limit spread.

Should I adopt a cat that has been diagnosed with calicivirus?

A cat that has recovered from feline calicivirus can make a wonderful companion. Most cats recover fully and live normal, healthy lives. If the cat is still in the acute phase or is a known carrier, discuss management strategies with your veterinarian — especially if you have other cats at home. Ensuring all cats in the household are up to date on their FVRCP vaccinations is the most important step. Visit our adoption page to meet cats ready for their forever homes.