Understanding Cat Flu Symptoms: A Comprehensive Guide for Pet Owners

“Cat flu” is the usual name for a contagious upper-respiratory infection in cats. People often look it up after a sudden burst of sneezing, sticky eyes, a blocked nose, or a cat that won’t eat. The stakes are mostly practical: congestion can stop a cat eating and drinking, and in young, old, or unwell cats it can tip into more serious illness.

Below is a clear, vet-aligned guide to what cat flu is, what it looks like, how it spreads, when to get help, and what recovery and prevention usually involve.

What cat flu is

Cat flu isn’t one single virus. It’s a syndrome (a set of signs) most commonly caused by feline herpesvirus-1 (FHV-1) and feline calicivirus (FCV).^{1, 2} Other infections can be involved as well, especially in crowded settings or where cats are under stress.¹

Most cases mainly affect the eyes, nose, mouth, and throat. Some cats recover quickly. Others develop longer-running problems, particularly with the eyes or sinuses, or they become carriers that can shed virus again later on.^{2, 3}

Symptoms of cat flu

Signs vary from mild to miserable. In many cats, it starts like a plain head cold and then becomes more obvious over a day or two.

Common signs

• Sneezing
• Runny or blocked nose
• Watery, sticky, or crusted eye discharge (conjunctivitis)
• Fever
• Loss of appetite (often because smell is dulled by congestion)
• Tiredness and low energy

^{3, 4}

Signs that can point to a specific cause

• Mouth ulcers can occur, particularly with FCV.^{1, 2}
• Eye pain, squinting, or corneal ulcers are classically linked with FHV-1.²

Severity varies

Kittens, older cats, and cats with other health problems tend to be hit harder. Crowding and stress (boarding, shelters, moving house, new pets) can also make outbreaks more likely and relapses more noticeable.^{1, 2, 3}

How cat flu spreads

Cat flu spreads through droplets (from sneezing and close contact) and from contaminated objects and hands (food bowls, bedding, carriers, your sleeves after cuddling a sick cat).^{1, 4}

Some cats remain carriers after they seem better. With FHV-1 especially, the virus can stay in the body for life and be shed again later, commonly around stressful events.^{2, 3} FCV can also be shed by recovered cats, and it tends to persist longer in the environment than herpesvirus, so cleaning matters.⁴

Diagnosis and when to see a vet

Vets often diagnose cat flu based on the pattern of signs and your cat’s history. In some situations (severe disease, recurring eye problems, outbreaks in multi-cat homes, shelters), your vet may recommend swabs and lab testing (such as PCR) to help identify the cause.²

Go promptly if you notice any of the following

• Laboured or open-mouth breathing, or your cat seems to be struggling for air
• Not eating for a day (or refusing food entirely), especially in kittens
• Not drinking, repeated vomiting, or signs of dehydration
• Marked lethargy, high fever, or rapid worsening over 24–48 hours
• Eye pain, a cloudy eye surface, squinting, or the eye held shut
• A kitten, an older cat, or a cat with another condition (such as heart disease) becoming unwell

^{3, 4}

Treatment options for cat flu

There’s no single “cure” for viral cat flu. Treatment is usually a mix of supportive care and targeted medication when needed.

What vets may use

• Supportive care to keep your cat eating, drinking, warm, and comfortable.²
• Antibiotics if a secondary bacterial infection is suspected (viruses don’t respond to antibiotics, but bacterial complications can).^{2, 1}
• Antiviral treatment in selected cases, especially for herpesvirus-related eye disease.²

Home care that often helps

• Keep the air warm and slightly humid. A steamy bathroom for a few minutes (with the cat safely in the room, not in the shower) can loosen nasal congestion.
• Gently clean eye and nose discharge with warm water and soft cotton pads, using a fresh pad each wipe.
• Make food easy to smell. Warm wet food slightly and offer small, frequent meals.
• Prioritise fluids. Offer fresh water often; wet food can help with hydration.
• Reduce stress and handling. Quiet room, predictable routine, and rest.

^{2, 3}

Prevention: vaccines and sensible hygiene

Vaccination is the main prevention tool. It doesn’t guarantee a cat won’t catch FHV-1 or FCV, but it usually reduces how severe the illness is and helps limit shedding, which protects other cats in the household and community.^{2, 3, 4}

In Australia, “core” cat vaccines are often referred to as the F3 vaccination (panleukopaenia plus cat flu: herpesvirus and calicivirus). Your vet will advise the right schedule for your cat’s age and risk, but guidelines commonly start at around 6–9 weeks of age with boosters until 16 weeks or older, then a booster at 12 months, then at intervals based on risk and vaccine type (often no more frequently than every three years for many cats).^{5, 6, 7}

Practical prevention in multi-cat homes

• Isolate unwell cats from others until fully recovered (often around two weeks, sometimes longer).³
• Don’t share bowls, litter trays, bedding, or grooming tools during illness.
• Wash hands between cats; clean and disinfect surfaces and carriers.
• Reduce stress where possible, especially for known herpesvirus carriers.

^{1, 3, 4}

Long-term effects and complications

Many cats recover fully. Some don’t, particularly after severe infection as kittens or when repeated flare-ups occur.

Possible complications

• Chronic or recurring eye disease (especially with herpesvirus), including keratitis and corneal ulcers.²
• Ongoing nasal inflammation with intermittent congestion and discharge, sometimes linked to chronic rhinitis after earlier infections.¹
• Pneumonia can occur, more commonly in vulnerable cats or with complications.^{1, 2}

Living with a cat flu “regular”

For cats that relapse, management is usually about keeping episodes small: vaccination kept current, early veterinary care for eye pain or appetite loss, and a calm environment that avoids unnecessary stressors where possible.^{2, 4}

Final thoughts

Cat flu is common, contagious, and often manageable, but it deserves respect. When a cat stops eating, can’t breathe comfortably through a blocked nose, or has painful eyes, the situation can shift quickly. A calm, warm recovery space at home helps, and early veterinary advice is what prevents the messy cases from becoming lasting ones.^{2, 3}

References

1. Merck Veterinary Manual: Feline Respiratory Disease Complex (professional)
2. Cornell Feline Health Center: Respiratory Infections (including feline herpesvirus and calicivirus)
3. RSPCA Australia Knowledgebase: What is cat flu and how is it managed?
4. RSPCA ACT: Cat vaccines — what are they for? (herpesvirus/calicivirus spread, environmental survival, vaccination effect)
5. WSAVA: Guidelines for the Vaccination of Dogs and Cats (feline vaccination table)
6. WSAVA: Vaccination Guidelines (2024 resources)
7. RSPCA Australia Knowledgebase: What vaccinations should my cat receive?
8. Cat Protection Society of NSW: Vaccinations factsheet (F3/core vaccine context in Australia)