FHV-1 vs Feline Calicivirus: How to Tell Them Apart

Key takeaway: FHV-1 (feline herpesvirus) and feline calicivirus (FCV) are two different viruses that both cause upper respiratory infection in cats, so the symptoms often overlap. FHV-1 tends to drive heavy sneezing, eye discharge, conjunctivitis, and corneal ulcers, while FCV is more often linked to mouth and tongue ulcers and drooling. Only your veterinarian, usually with testing, can confirm which one your cat has, and that matters because the two use different treatments.

A cat resting comfortably at home.

What is the difference between FHV-1 and feline calicivirus?

FHV-1 and feline calicivirus (FCV) are two separate viruses that are among the leading causes of cat upper respiratory infection. FHV-1 is a herpesvirus, also called feline viral rhinotracheitis or "cat flu", and it is a lifelong infection that flares up under stress. FCV is a calicivirus that is closely associated with mouth ulcers, drooling, and chronic oral disease.

Because both viruses spread in multi-cat homes, shelters, and boarding settings across the Gulf, many caregivers see sneezing or discharge and cannot tell which one is responsible. The infections can even occur together, which makes a clear diagnosis important.

They are not the same virus, they do not use the same product, and neither one is the same as FIP. Getting the label right guides the right care plan.

How can you tell FHV-1 from feline calicivirus by symptoms?

You usually cannot tell FHV-1 from feline calicivirus (FCV) by symptoms alone with full certainty, but the pattern of signs points you in a direction. FHV-1 leans toward the eyes and nose, with squinting, conjunctivitis, and corneal ulcers, while FCV leans toward the mouth, with tongue and gum ulcers and drooling.

The table below summarizes the tendencies that vets look at. Use it as a guide, not a diagnosis.

Feature	FHV-1 (herpesvirus)	FCV (feline calicivirus)
Common name	Feline viral rhinotracheitis, cat flu	Feline calicivirus
Eyes	Conjunctivitis, corneal ulcers, squinting	Eye involvement less common
Nose	Heavy sneezing, nasal discharge	Sneezing, nasal discharge
Mouth	Occasional mouth ulcers	Mouth and tongue ulcers, drooling
Course	Lifelong, stress-triggered flare-ups	Can persist; linked to chronic gingivostomatitis

The overlap is real, so a cat with sneezing and eye discharge could have either virus, or both. When mouth ulcers and drooling dominate, FCV moves up the list. When the eyes are the main problem, FHV-1 moves up.

What are the symptoms of feline herpesvirus (FHV-1)?

Feline herpesvirus (FHV-1) most often causes sneezing, nasal and eye discharge, squinting, conjunctivitis, and corneal ulcers, with mouth ulcers appearing only occasionally. FHV-1 is a lifelong infection, so many cats look healthy between episodes and then flare up when they are stressed.

Triggers in the Gulf can include boarding, travel, a new pet, moving home, or any change that raises stress. During a flare, the eyes and upper airways are usually the first to show signs.

The eye signs deserve special attention, because untreated corneal ulcers can threaten vision. Our detailed guide to FHV-1 eye problems, conjunctivitis, and corneal ulcers explains what to watch for and when eye pain needs urgent veterinary care.

For a broader look at the pattern of episodes and what sets them off, see our overview of feline herpesvirus symptoms and triggers.

Care for FHV-1 focuses on reducing and managing flare-ups, not on eliminating the virus. FHV-1 stays with the cat for life, and the goal is fewer, milder episodes and comfortable eyes and breathing.

What are the symptoms of feline calicivirus (FCV)?

Feline calicivirus (FCV) classically causes mouth and tongue ulcers, drooling, and reluctance to eat, along with sneezing and nasal discharge. FCV is a common cause of painful oral disease, and in some cats it is linked to feline chronic gingivostomatitis, a severe inflammation of the mouth.

Because the ulcers are painful, one of the earliest signs many caregivers notice is a cat that stops eating or drops food. If your cat is drooling or turning away from meals, our guide to feline calicivirus mouth ulcers and why your cat won't eat walks through what to do.

FCV can also become a chronic problem in the mouth. To understand the connection between FCV and long-term oral inflammation, read our article on feline chronic gingivostomatitis (FCGS) and FCV.

For a full Gulf-focused overview of the disease, including at-home support and prevention, see our guide to feline calicivirus in cats.

Why does it matter which respiratory infection your cat has?

It matters because FHV-1 and feline calicivirus (FCV) are treated with different products and different strategies, so the correct diagnosis shapes the whole plan. FHV-1 care is built around managing flare-ups over the cat's life, while FCV care often centers on the mouth and on antiviral support.

Antibiotics do not treat either virus itself. They only address secondary bacterial infections that can ride along with a viral flare, which is why a vet decides if and when they are needed.

The stakes are highest with the eyes and the mouth. FHV-1 corneal ulcers can threaten sight, and FCV oral ulcers can be painful enough to stop a cat eating, so identifying the driver helps target relief where the cat needs it.

A confirmed diagnosis also prevents wasted time. Reaching for the wrong product delays real relief, so evidence, not guesswork, should guide the choice.

How are FHV-1 and feline calicivirus treated in the Gulf?

FHV-1 and feline calicivirus (FCV) each have a veterinarian-prescribed antiviral option, and the two are not interchangeable. For FHV-1, the famciclovir option in this market is HerpX. For FCV oral disease, the EIDD-1931 based CaliciX line is the positioned product.

Virus	Veterinarian-prescribed option	Active ingredient	Dosing
FCV	EIDD-1931 Oral Capsules (CaliciX line)	EIDD-1931	1 capsule (15 mg) per 2.5 kg body weight, every 12 hours; 60 capsules per bottle; standard 60 days; AED149.00
FHV-1	HerpX	famciclovir	Dose set by your veterinarian

A few important limits apply to the EIDD-1931 Oral Capsules. They are not for ocular or neurological cases, or for cats that are not eating or defecating, and EIDD-1931 is teratogenic, so it must not be used in pregnant or lactating queens.

For HerpX, dosing and strength are decided by your veterinarian, so we do not publish a dose number here. Your vet will match the plan to your cat.

There is no published success percentage for FHV-1 treatment, so any figure you see quoted for it should be treated with caution. Care for FHV-1 is measured in fewer and milder flare-ups, not in a claim to clear the virus, because FHV-1 is never eliminated from the body.

Whatever the diagnosis, start with your veterinarian. Testing, an exam, and a proper history separate FHV-1 from FCV and rule out other causes before any antiviral begins.

Are FHV-1 and feline calicivirus the same as FIP?

No. FHV-1 and feline calicivirus (FCV) are respiratory and oral viruses, while Feline Infectious Peritonitis ("FIP") is a separate, far more serious disease caused by a mutated feline coronavirus. FIP is not a cause of ordinary cat flu, and it uses a completely different treatment.

FIP treatment is built around GS-441524, the antiviral at the core of modern FIP care, with a 92% success rate reported by UC Davis (Pedersen, 2019) for the injectable monotherapy. This is a different product family from the respiratory and oral virus options above, and the figure applies only to FIP, never to FHV-1 or FCV.

The CureFIP network has supported more than 100,000 cats since 2019 across FIP care, which is why we are careful to keep these conditions clearly separated. If you are worried about FIP specifically, our step by step guide to how FIP is diagnosed explains the process.

FAQ

Can a cat have both FHV-1 and feline calicivirus at once?

Yes. A cat can be infected with both FHV-1 (herpesvirus) and feline calicivirus (FCV) at the same time, which is one reason symptoms overlap and a veterinary diagnosis matters. Your veterinarian can use an exam and testing to identify which viruses are involved.

Is feline herpesvirus (FHV-1) curable?

No. FHV-1 is a lifelong infection that is never cleared or eliminated from the body, so care focuses on reducing and managing flare-ups rather than removing the virus. With good management, many cats have fewer and milder episodes over time.

Do antibiotics treat FHV-1 or feline calicivirus?

Antibiotics do not treat either virus itself. They only address secondary bacterial infections that can accompany a viral flare, and your veterinarian decides if and when they are appropriate.

Which product is used for feline calicivirus mouth disease?

For feline calicivirus (FCV) oral disease, the EIDD-1931 based CaliciX line is the positioned option, dosed at 1 capsule (15 mg) per 2.5 kg body weight every 12 hours for a standard 60 days, at AED149.00. It is not for ocular or neurological cases, or for cats that are not eating or defecating, and it must not be used in pregnant or lactating queens.

How do I know if it is FIP and not just cat flu?

FHV-1 and FCV cause respiratory and oral signs, while Feline Infectious Peritonitis ("FIP") is a separate coronavirus disease that needs its own diagnosis and GS-441524 based treatment. If you are concerned, your veterinarian can run the tests that tell these conditions apart.

If your cat is sneezing, has eye trouble, or has stopped eating, the safest next step is a conversation with a professional who can confirm the diagnosis. To learn more about the available options and to talk with our team or your own veterinarian, reach out to the CureFIP Gulf team for guidance tailored to your cat.