Understanding Cat Flu Symptoms: A Comprehensive Guide for Pet Owners

By Sophie Kininmonth · 24 Dec 2025 (updated 21 Jul 2026) ·6 min read

Cat flu is the everyday name for a contagious upper-respiratory infection in cats, and it is one of the most common reasons owners search for answers after a sudden run of sneezing, sticky eyes, a blocked nose, or a cat that has gone off its food. Most cases behave like a bad head cold and settle with good home care and a bit of patience. The catch is practical rather than dramatic: a congested cat can stop eating and drinking, and in kittens, older cats, or cats with other health problems that can tip into something more serious. Below is a clear, vet-aligned guide to what cat flu is, how to spot it, how it spreads, when to call the vet, and how recovery and prevention usually work.

What cat flu is

Cat flu is not a single virus. It is a syndrome, a set of signs, most commonly caused by feline herpesvirus-1 (FHV-1) and feline calicivirus (FCV).^{1, 2} Other infections can join in too, especially where cats are crowded or under stress.¹

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

Symptoms of cat flu

Signs range from mild to miserable, and they often build over a day or two rather than arriving all at once.

Common signs

Sneezing
Runny or blocked nose
Watery, sticky, or crusted eye discharge (conjunctivitis)
Fever
Loss of appetite, often because congestion has dulled the cat's sense of smell
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 from boarding, shelters, moving house, or a new pet can 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 through contaminated objects and hands: food bowls, bedding, carriers, and your sleeves after cuddling a sick cat.^{1, 4}

Some cats stay carriers after they look better. With FHV-1 especially, the virus can remain 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 survive longer in the environment than herpesvirus, so cleaning matters.⁴

Diagnosis and when to see a vet

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

Go promptly if you notice any of the following

Laboured or open-mouth breathing, or a cat that 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 to 48 hours
Eye pain, a cloudy eye surface, squinting, or an 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 is no single cure for viral cat flu. Treatment is usually a mix of supportive care and targeted medication when it is 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 do not respond to antibiotics, but the bacterial complications that follow them 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 and 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 for each wipe.
Make food easy to smell. Warm wet food slightly and offer small, frequent meals.
Prioritise fluids. Offer fresh water often, and remember wet food helps with hydration.
Reduce stress and handling. A quiet room, a predictable routine, and rest.

^{2, 3}

Prevention: vaccines and sensible hygiene

Vaccination is the main prevention tool. It does not guarantee a cat will never 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, the core cat vaccine is often called the F3 (panleukopaenia plus cat flu, meaning herpesvirus and calicivirus). Your vet will set the right schedule for your cat's age and risk, but guidelines commonly start at around 6 to 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 than every three years for many cats).^{5, 6, 7}

Practical prevention in multi-cat homes

Isolate unwell cats from the others until fully recovered, often around two weeks and sometimes longer.³
Do not share bowls, litter trays, bedding, or grooming tools during illness.
Wash hands between cats, and clean and disinfect surfaces and carriers.
Reduce stress where you can, especially for known herpesvirus carriers.

^{1, 3, 4}

Long-term effects and complications

Many cats recover completely. Some do not, particularly after a severe infection as a kitten or when flare-ups keep coming back.

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, more commonly in vulnerable cats or where complications set in.^{1, 2}

Living with a cat flu regular

For cats that relapse, the aim is to keep each episode small: vaccination kept current, early veterinary care for eye pain or appetite loss, and a calm environment that avoids unnecessary stressors.^{2, 4}

The Bottom Line

Cat flu is common, contagious, and usually manageable, but it deserves respect. When a cat stops eating, cannot breathe comfortably through a blocked nose, or has painful eyes, the picture can change fast. A calm, warm recovery space at home does a lot of the work, and early veterinary advice is what keeps the messy cases from turning into lasting ones.^{2, 3}

References

Sophie Kininmonth

Dog lover and writer at My Pets Australia, sharing practical breed guides and care advice for Australian pet owners.