Feline calicivirus (FCV) is one of the most common upper respiratory viruses in cats, causing oral ulcers, sneezing, and nasal discharge. Vaccination reduces disease severity, and most healthy cats recover fully — but a virulent systemic strain (VS-FCV) causes a severe, life-threatening disease requiring intensive care. Knowing which type you're dealing with changes the urgency dramatically.
Last reviewed: June 2026
What Is Feline Calicivirus?
Feline calicivirus (FCV) is a highly contagious RNA virus and one of the two primary causes of upper respiratory infection (URI) in cats, alongside feline herpesvirus-1. FCV is shed in oral and nasal secretions and spreads through direct contact, shared food and water bowls, grooming, and environmental contamination. The virus is environmentally stable for days to weeks on surfaces.
FCV exists as multiple strains with varying virulence. Most strains cause mild to moderate upper respiratory disease with a characteristic feature: oral ulcers on the tongue, hard palate, or nose. The calicivirus vaccine is part of the core feline vaccination protocol recommended by the AAFP-AAHA Feline Life Stage Guidelines, 2021, though no single vaccine protects against all strains.
Classic vs. Virulent Systemic FCV
Classic FCV causes the typical URI syndrome: sneezing, nasal discharge, conjunctivitis, and oral ulcers. Fever is common. Most healthy adult cats recover within 1–3 weeks with supportive care. Kittens and immunocompromised cats may have more severe disease.
Virulent systemic FCV (VS-FCV) is a rare but severe form in which novel FCV strains cause disease beyond the respiratory tract. Signs include high fever, facial and limb edema (swelling), skin ulceration, jaundice, and multi-organ failure. Mortality rates in VS-FCV outbreaks have been reported at 33–50%, even in vaccinated adult cats. VS-FCV has been associated with recent vaccination or visits to veterinary facilities in some outbreak investigations, though the mechanism is not fully understood. Any cat showing edema, jaundice, or skin sloughing alongside URI signs should be treated as a potential VS-FCV case.
Signs of Calicivirus in Cats
Classic FCV:
- Sneezing, nasal discharge (clear to mucopurulent)
- Ulcers on the tongue, lips, hard palate, or nasal planum — the most distinguishing feature of FCV vs. herpesvirus
- Eye discharge and conjunctivitis
- Fever (103–106°F / 39.4–41.1°C)
- Lethargy and reduced appetite
- Occasional limping — FCV can cause a brief, self-limiting polyarthritis ("limping kitten syndrome")
VS-FCV (requires urgent emergency care):
- High fever plus facial or limb swelling
- Skin ulceration on face, pinnae, or limbs
- Yellow discoloration of skin, gums, or eyes (jaundice)
- Rapid deterioration within 24–48 hours
Treatment
Classic FCV: Treatment is primarily supportive. Appetite stimulants, syringe feeding or feeding tube placement, oral rinsing with dilute chlorhexidine, and nasal decongestants to improve smell and appetite are the mainstays. Antibiotics are used when secondary bacterial infection is suspected. Lysine supplementation, once common, has not been shown to reduce FCV shedding in studies and is no longer routinely recommended for calicivirus.
VS-FCV: Requires intensive hospitalization with IV fluids, antibiotics (to prevent secondary infections), anti-inflammatory drugs, nutritional support, and wound care. Despite aggressive treatment, prognosis is guarded to poor.
According to the AAFP Senior Care Guidelines, 2021, senior cats with FCV URI may require more aggressive nutritional support earlier because appetite loss in older cats poses a higher risk of hepatic lipidosis.
Vaccination
The core FVRCP vaccine includes protection against feline viral rhinotracheitis (herpesvirus), calicivirus, and panleukopenia. Vaccination significantly reduces the severity of clinical disease even when it does not completely prevent infection. Kittens receive a series starting at 6–8 weeks of age; boosters are given per AAFP-AAHA recommendations.
What Does Treatment Cost?
Mild FCV in a healthy adult cat: a vet exam runs $50–150; appetite stimulants and supportive medications add $30–80. Hospitalization for cats not eating or with severe URI costs $200–500/day. VS-FCV cases requiring intensive care can cost $1,500–5,000+. Prevention via FVRCP vaccination is $25–60 per dose.
When to See a Vet
Call your vet today if:
- Your cat has mouth ulcers, painful swallowing, or is drooling excessively
- Your cat has not eaten for more than 24 hours
- Sneezing has been accompanied by thick, colored nasal discharge for more than 3 days
Go to the ER immediately if:
- Your cat has swelling of the face or legs alongside URI signs
- Your cat's gums or skin appear yellow
- Your cat is having extreme difficulty breathing
- Rapid deterioration occurs within 24–48 hours of illness onset
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Frequently Asked Questions
How long does calicivirus last in cats? Classic FCV URI typically resolves within 1–3 weeks in healthy adult cats with supportive care. Kittens, senior cats, and immunocompromised cats may take longer. Some cats become chronic carriers and intermittently shed the virus throughout their lives, particularly during stress.
Can cats spread calicivirus to dogs or humans? No. Feline calicivirus is species-specific and cannot infect dogs or humans. In multi-cat households, infected cats shed virus in their saliva and nasal secretions — separate food bowls, water sources, and litter boxes reduce transmission.
Does the calicivirus vaccine fully protect cats? Vaccination significantly reduces disease severity but does not provide complete protection against all strains — FCV mutates rapidly and multiple strains circulate. A vaccinated cat can still get FCV but typically has much milder disease and recovers faster than an unvaccinated cat.
How much does treating calicivirus cost in cats? Mild cases cost $50–230 for an exam and supportive medications. Hospitalization for anorexic or severely ill cats runs $200–500/day. Virulent systemic FCV cases can cost $1,500–5,000 or more in intensive care. Prevention through vaccination is $25–60 per booster.
My cat has a mouth sore and is sneezing — do I need the vet today? Oral ulcers with sneezing strongly suggest FCV. A vet visit is appropriate within 24 hours — cats with mouth ulcers are often too painful to eat, putting them at risk of hepatic lipidosis if they go without food. Same-day or next-day evaluation is recommended rather than waiting.
Still Not Sure if Your Cat Needs a Vet?
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