Cat flu: symptoms, causes and treatment

If your cat has started sneezing, has weepy eyes or a runny nose, it's natural to worry. "Cat flu" is one of the most common reasons cats end up at the vet, and while it can look alarming, most adult cats recover well with the right care at home and, where needed, from your vet. Kittens, elderly cats and those with other health problems are more vulnerable, so it's worth knowing what to look for and when to act quickly.

Cat flu isn't actually influenza. It's the everyday name for a group of upper respiratory infections in cats, most often caused by one of two viruses. Understanding the difference matters, because it explains why cat flu can keep coming back even after your cat seems to have recovered, and why vaccination is such an important part of prevention.

This guide explains what causes cat flu, the symptoms to watch for, how it's treated, how contagious it is, and what you can do to protect your cat.

What is cat flu?

Cat flu is the name given to a highly contagious upper respiratory tract infection in cats. It behaves much like a human cold, causing sneezing, a runny nose and sore, weepy eyes, but it can be more serious in cats than a cold usually is in people. According to Cats Protection, cat flu is spread much like a human cold: through an infected cat coughing or sneezing, with other cats then picking up the germs from the air, from shared surfaces, or from direct contact.

It isn't usually life-threatening in healthy adult cats, but it can be serious, and occasionally fatal, in kittens, older cats, and cats with other underlying illnesses or weakened immune systems, according to Blue Cross.

What causes cat flu

Cat flu is not one single illness. It's usually caused by one of two viruses, sometimes both at once:

• Feline herpesvirus (FHV-1) – this typically causes more severe upper respiratory disease and is a common cause of eye problems in cats, including conjunctivitis and corneal ulcers (painful defects on the surface of the eye).
• Feline calicivirus (FCV) – this is highly contagious and tends to cause a milder respiratory illness, but it's also strongly linked with mouth ulcers and oral pain.

Both viruses spread easily between cats through saliva and discharge from the nose and eyes. An infected cat sneezing can spray viral particles a surprising distance, and the virus can also survive for a time on shared bowls, bedding, litter trays and even on your hands and clothing, which is why multi-cat households, catteries, rescue centres and breeding colonies see outbreaks so often.

Occasionally, secondary bacterial infections take hold once the viral infection has weakened a cat's defences, which is one reason antibiotics sometimes form part of treatment even though they don't touch the underlying virus itself.

Symptoms to watch for

The signs of cat flu are similar to a cold or flu in humans, but usually more pronounced. Common symptoms, drawn from PDSA and Cats Protection advice, include:

• Sneezing, sometimes frequent and in bouts
• A runny or blocked nose
• Weepy, sore or red eyes, sometimes with a discharge
• Dribbling or drooling
• Mouth ulcers, which can make eating painful
• Reduced or lost appetite
• Fever
• Lethargy or sleeping more than usual
• A cough

In more severe cases, cats can develop eye ulcers, which are painful defects on the surface of the eye and need urgent veterinary attention to avoid lasting damage. Because cat flu often affects a cat's sense of smell, many cats stop eating simply because their food no longer smells appealing, not because they feel too unwell to eat. This matters because reduced eating and drinking can quickly lead to dehydration, particularly in small or already poorly cats.

Why kittens are at greater risk

Kittens are especially vulnerable to cat flu because their immune systems aren't yet fully developed, according to PDSA's kitten-specific advice. In severe cases, cat flu in kittens can progress to pneumonia, breathing difficulties or joint pain, and without treatment it can be life-threatening. Kittens who lose their appetite for more than a day or two are at real risk of dehydration and low blood sugar, so prompt veterinary care is important rather than a wait-and-see approach.

Most healthy kittens can have their first vaccination against cat flu from around eight to nine weeks old, with a second dose given a few weeks later to build full protection.

How vets diagnose cat flu

In most cases, your vet will diagnose cat flu from a clinical examination and your description of your cat's symptoms; the combination of sneezing, discharge, mouth ulcers and lethargy is usually distinctive enough. If your cat isn't responding to treatment as expected, has repeated flare-ups, or your vet suspects a different underlying cause, they may take swabs from the mouth, nose or eyes to identify exactly which virus (or combination of viruses) is involved, or to rule out a secondary bacterial infection.

How cat flu is treated

There's no specific cure for cat flu, because it's caused by a virus, and, as with the human cold, treatment focuses on supporting your cat while their body fights the infection and relieving their symptoms. According to PDSA, treatment options your vet may use include:

• Lubricating and antibiotic eye drops – soothing drops to protect sore eyes, with antibiotic drops added if a bacterial eye infection is suspected.
• Antibiotics – these don't act on the virus itself, so they're only given if your vet believes a secondary bacterial infection has developed.
• Anti-inflammatories and decongestants – to ease swelling and help your cat breathe more comfortably, as noted by Blue Cross.
• Antivirals – these can help speed up recovery in some cases, but need three to four weeks of treatment, aren't always effective, and tend to be considerably more expensive than other options.
• Hospitalisation and supportive care – cats with severe symptoms, or who stop eating and drinking, may need fluids via a drip and more intensive nursing care in a veterinary hospital. In serious cases, oxygen support may be needed.

Caring for your cat at home

Alongside any veterinary treatment, there's a lot you can do at home to keep your cat comfortable:

• Gently wipe away discharge from the eyes and nose using a cotton wool pad soaked in warm water, using a fresh pad for each eye to avoid spreading infection.
• Encourage eating by warming your cat's food slightly and choosing something with a strong smell, since a blocked nose often puts cats off food that would normally tempt them.
• Sit with your cat in a steamy room, for example the bathroom while you shower, as the moist air can help loosen thick mucus and ease breathing.
• Keep your cat warm, calm and away from draughts, and minimise stress where you can, since stress is closely linked to flare-ups.
• Keep fresh water easily accessible, and monitor how much your cat is drinking and eating so you can flag any concerns to your vet quickly.

Cat flu often blunts a cat's sense of smell, so warming food and choosing something aromatic can make all the difference to whether they'll eat.

If you're also managing your cat's weight or appetite through recovery, our Pet Calorie Calculator can help you keep track of what they need day to day.

Why some cats become lifelong carriers

One of the trickier aspects of cat flu is that many cats never fully clear the virus, particularly feline herpesvirus. Cats Protection notes that once a cat has recovered from cat flu, some will continue to harbour the infection and can develop symptoms again later, particularly at times of stress or other illness. This is often described as being a "carrier": the virus becomes dormant in the body and can reactivate, sometimes without the cat ever fully falling ill again, and sometimes triggering a fresh bout of visible symptoms.

Common triggers for a flare-up in a carrier cat include the stress of a vet visit, a house move, a new pet or person in the household, or another illness lowering their defences. This is worth knowing so that a sudden return of sneezing or sore eyes in a cat that's had flu before doesn't come as a complete surprise, and so you can try to keep stressful changes as gentle and gradual as possible for a cat prone to flare-ups.

How contagious is cat flu, and how to stop it spreading

Cat flu spreads easily between cats, through direct contact, airborne droplets from sneezing, and shared surfaces like food bowls, litter trays and bedding. If you have more than one cat and one becomes unwell:

• Keep the infected cat isolated from your other cats as much as is practical.
• Use separate food and water bowls, litter trays and bedding for the unwell cat.
• Disinfect shared items thoroughly (check any cleaning product is safe for use around cats) after the infected cat has been in contact with them.
• Wash your hands between handling cats, since the virus can be carried on hands and clothing.

Reassuringly, cat flu is species-specific: cats cannot pass it to humans, dogs, or other non-feline pets, and cats cannot catch human flu from you.

Vaccination and prevention

Vaccination is the single most effective step you can take to protect your cat. Cat flu vaccines are given as standard as part of the core kitten vaccination course, usually starting from around eight to nine weeks old, with a second dose roughly three to four weeks later to build proper protection, followed by regular boosters throughout your cat's life.

It's important to understand what vaccination can and can't do. It doesn't guarantee your cat will never catch cat flu, but it significantly reduces the severity of symptoms if they do become infected, and lowers the chances of your cat needing intensive treatment or hospitalisation. Cats in higher-risk environments, such as multi-cat households, those with regular outdoor access, or cats who go into catteries or boarding, may benefit from more frequent boosters; your vet can advise on the right schedule for your individual cat.

Beyond vaccination, reducing stress, avoiding overcrowding, and limiting contact with unfamiliar or unwell cats all help lower the risk, particularly for cats who are already carriers of the virus.

If you're weighing up whether your household and lifestyle are ready for a cat, especially one that may need ongoing veterinary care, our Pet Ownership Quiz can help you think it through before you commit.

When to see your vet

Contact your vet promptly if your cat shows any signs of cat flu, rather than waiting to see if it clears up on its own. Cat flu can, in some cases, lead to lasting problems including damaged eyes, pneumonia, or long-term damage to the nose and sinuses, so early treatment gives your cat the best chance of a full recovery.

Treat it as urgent, and seek same-day veterinary advice, if your cat:

• Stops eating or drinking, even for a day
• Seems very lethargic, weak, or is struggling to breathe
• Has eyes that appear cloudy, very swollen shut, or painful
• Is a kitten, an elderly cat, or has another underlying health condition
• Shows no improvement, or gets worse, after a few days of home care

When in doubt, it's always safer to call your vet for advice than to wait.

*This is general guidance, not a substitute for advice from your vet, who can assess your individual pet.*

Sources

• PDSA — cat flu symptoms, causes and treatment (pdsa.org.uk).
• PDSA — cat flu in kittens: risks, symptoms and treatment (pdsa.org.uk).
• Cats Protection — what is cat flu and how you can treat it (cats.org.uk).
• Blue Cross — cat flu: symptoms, causes and treatment (bluecross.org.uk).
• Vets Now — cat flu and sneezing in cats, causes and when to seek help (vets-now.com).