What is cat flu?
Updated By PetymFacts checked against official sources on
Quick answer
Cat flu is the everyday name for an upper respiratory infection in cats. More than 90% of cases are caused by feline herpesvirus, feline calicivirus or both. Cats sneeze, have runny eyes and nose and may stop eating. Most recovered cats remain carriers, and stress can bring the virus back. Vaccination usually prevents severe disease.
Also called feline upper respiratory infection, feline upper respiratory disease, URI in cats, feline herpesvirus, feline calicivirus.
Key facts
- More than 90% of upper respiratory infections in cats are thought to be caused by feline herpesvirus, feline calicivirus or both. International Cat Care
- It spreads by direct contact and on clothing, food bowls and other objects. International Cat Care
- Most cats that recover become carriers, and some shed the virus again at times of stress. International Cat Care
- Herpesvirus and calicivirus vaccines are core for every cat; they reduce how sick a cat gets but may not prevent infection. WSAVAstudy
- WSAVA suggests a cat-flu booster 1 to 2 weeks before the main yearly stay for cats that board. WSAVAstudy
What causes cat flu, and how do the two viruses differ?
The two viruses overlap, and only a vet's tests can say which a cat has. Bacteria often join in as a second infection.
| Feline herpesvirus (FHV-1) | Feline calicivirus (FCV) | |
|---|---|---|
| Typical signs International Cat Care | Sneezing, discharge, more severe eye disease | Sneezing, discharge, ulcers on the tongue, sore throat |
| After recovery International Cat Care | Most cats stay carriers for life; the virus hides and can flare up | Most cats shed the virus for weeks or months |
| Vaccine on the card WSAVAstudy | The R (rhinotracheitis) in FVRCP | The C in FVRCP |
What are the signs of cat flu?
Sneezing, a runny nose and watery or sticky eyes, red eyes with a lot of blinking, a fever, low energy and a reduced appetite. Calicivirus can cause painful ulcers on the tongue, so a cat may drool, paw at its mouth or go to the food bowl and walk away.
Affected cats often lose some of their sense of smell and find eating uncomfortable, so they become reluctant to eat, and a cat that does not eat recovers more slowly; some need hospital care and tube feeding. Any cat with these signs should see a vet, and a kitten, an older cat or a cat that has stopped eating should be seen quickly.
Why does cat flu come back after boarding or stress?
Herpesvirus does not leave the body. It hides, and stress, illness or a change of routine can wake it so the cat sheds virus and may show signs again. Moving house, a new pet, a cattery stay or a sitter's home can all be triggers, and a carrier can pass the virus to other cats while looking well.
That is why WSAVA advises that cats which board regularly may need the herpesvirus and calicivirus parts of their vaccine as often as every year, and suggests the booster 1 to 2 weeks before the main yearly stay. Care at home with a sitter keeps a cat in its own surroundings, which removes one change of routine (Petym's practical advice from these sources).
How do you nurse a cat with cat flu?
Follow your vet's treatment plan, and keep the cat warm, clean and comfortable. Clean discharge away from the eyes and nose often, for the cat's comfort, and use any eye drops exactly as prescribed. Soft, strong-smelling food that has been gently warmed can tempt a cat whose nose is blocked. Keep a sick cat away from other cats, with its own bowls and litter tray, and wash your hands after handling it.
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Questions owners ask
Can cat flu spread to my other cats?
- Yes. It spreads by direct contact with a sick cat and on clothing, food bowls and other objects, and carriers can shed virus while looking well. Keep a sneezing cat apart with its own bowls and litter tray, wash your hands after handling it, and ask your vet whether the other cats are up to date.
Does the cat flu vaccine stop my cat getting cat flu?
- Not completely. The herpesvirus and calicivirus vaccines usually prevent severe disease but may not stop infection, so a vaccinated cat can still have a mild cold. WSAVA treats both as core vaccines for every cat, including indoor cats.
How long does cat flu last?
- The Merck Veterinary Manual says signs last 5 to 10 days in milder cases and up to 6 weeks in severe ones; it varies with the virus, the cat's age and any second bacterial infection. Most cats stay carriers afterwards, and herpesvirus can flare up again under stress, so signs may return months later.
When is cat flu an emergency?
- When a cat stops eating, struggles to breathe, is very dull, or is a young kitten or an old cat. A cat that refuses food recovers more slowly and may need hospital care and feeding support. Call your vet the same day in any of these cases.
Keep reading
Related terms
More in health conditions
- ArthritisArthritis, or osteoarthritis, is a long-term joint disease in which worn cartilage lets the joint surfaces rub, causing stiffness, swelling and pain. It is very common in older dogs and cats. It cannot be cured, but pain relief from a vet, a healthy weight, gentle regular exercise and a few home changes keep most pets comfortable for years.
- Bloat (GDV)Bloat, or gastric dilatation-volvulus (GDV), is when a dog's stomach fills with gas and twists on itself, cutting off its blood supply. It mainly affects large and giant deep-chested breeds. Unproductive retching, a swelling belly, drooling and restlessness are the signs. It is a surgical emergency that can kill within hours.
- BOASBOAS, brachycephalic obstructive airway syndrome, is a breathing disorder of flat-faced dogs. Narrow nostrils, an overlong soft palate and a small windpipe block airflow, so affected dogs snore, snort, tire quickly and overheat easily. It is worse in heat, humidity and obesity. Surgery can widen the airway, and a lean weight helps.
- Canine distemperCanine distemper is a serious viral disease of dogs that can attack the skin, airways, gut and nervous system. It spreads in droplets from coughing, sneezing and barking, and through body fluids. There is no specific cure, and some dogs do not survive even with treatment. The D in the DHPPi vaccine prevents it.
- Canine parvovirusCanine parvovirus, or parvo, is a highly contagious virus that attacks a dog's gut and immune system. It spreads through infected faeces, survives a long time in the environment and hits unvaccinated puppies between 6 weeks and 6 months hardest. Vomiting and bloody diarrhoea can kill within days, and it is prevented by the core vaccine.
- Cherry eyeCherry eye is when the tear gland inside a dog's third eyelid slips out of place and shows as a smooth, red, cherry-like lump in the inner corner of the eye. It is common in young Bulldogs, Beagles, Shih Tzus and Pugs, and needs a vet, usually for surgery to put the gland back.
- Chronic kidney diseaseChronic kidney disease (CKD) is a slow, lasting loss of kidney function, common in older cats and also seen in older dogs. Early on there are often no signs; later a pet drinks and urinates more, eats less and loses weight. It cannot be cured, but a kidney diet, water and regular checks can slow it.
- DehydrationDehydration means a pet's body has lost more water than it has taken in, through heat, panting, vomiting, diarrhoea or illness. Early on the gums turn sticky; then the skin loses its spring and the eyes sink. A mildly dehydrated pet needs water and a watchful eye; a weak, vomiting or collapsing one needs a vet now.
- Dental diseaseDental disease in pets is mostly periodontal disease: plaque bacteria inflame the gums (gingivitis) and then destroy the tissue and bone holding the teeth (periodontitis). It is the most common disorder vets diagnose in dogs, and very common in cats. Bad breath, tartar and red gums are the early signs. Daily brushing prevents most of it.
- Diabetes in petsDiabetes mellitus is a lifelong condition in which a dog or cat cannot make or use enough insulin, so sugar builds up in the blood. Signs are drinking and peeing more, hunger and weight loss. Most diabetic pets live well on insulin injections given at set times with meals, and some cats go into remission.
Keep exploring
Sources
Each source was opened and read on the date shown. How Petym checks its sources
- International Cat Care: Cat flu (upper respiratory infection) (opens in a new tab)
- International Cat Care: Feline herpesvirus (FHV) (opens in a new tab)
- European Advisory Board on Cat Diseases (ABCD): Guideline for feline herpesvirus infection (opens in a new tab)
- European Advisory Board on Cat Diseases (ABCD): Guideline for feline calicivirus infection (opens in a new tab)
- Merck Veterinary Manual: Feline respiratory disease complex (opens in a new tab)
- WSAVA: Core and non-core vaccines for pet cats (opens in a new tab)
- WSAVA: 2024 guidelines for the vaccination of dogs and cats (WSAVA Vaccination Guidelines Group, Journal of Small Animal Practice) (opens in a new tab)