Cat flu: signs, treatment, vaccination and recovery

Cat flu is a common name for contagious infections affecting a cat's nose, throat, eyes and mouth. It is a disease complex rather than one single virus.

Feline herpesvirus and calicivirus are leading causes, while bacteria and mixed infections can influence the signs. Despite the familiar name, it is not the same illness as seasonal human influenza. [1]

Most cases involve feline herpesvirus, feline calicivirus or both. Chlamydia felis, Mycoplasma species and Bordetella can cause or complicate particular eye and respiratory presentations.

The likely organisms vary with age, vaccination, housing and outbreaks. Identifying one agent does not always prove it is the only reason that cat is ill. [1]

The main feline herpesvirus and calicivirus infections are adapted to cats and pose no known human risk. Ordinary cat flu is not passed to people or dogs like a shared seasonal cold.

Some less common bacterial agents deserve normal hygiene precautions, particularly around eye discharge. A vet or doctor can advise households with vulnerable people when a specific organism has been identified. [1]

Infectious droplets and secretions can pass through close contact, sneezing and contaminated hands, bowls, bedding or surfaces. Cats can therefore transmit infection without sharing the same room at the same moment.

Crowding and frequent introductions increase opportunities for spread. The survival of each agent outside the cat differs, so cleaning and separation plans need to account for the suspected organism and setting. [1]

Young kittens, older cats, cats with weakened immunity and those in crowded multi-cat settings can become more seriously unwell. Eye injury, pneumonia, dehydration and failure to eat are particular concerns.

Vaccination reduces severe disease but does not make every cat fully infection-proof. Risk also rises when a cat is stressed, newly rehomed or already managing another illness. [2]

Common signs include sneezing, runny or blocked nose, watery or sore eyes, fever, drooling, mouth ulcers, tiredness and reduced appetite. Some cats also cough.

Different agents create overlapping patterns, and the same infection can be mild in one cat but serious in another. Eye pain, breathing effort or poor intake changes the urgency. [1]

Feline herpesvirus commonly affects both the upper airways and eyes, causing sneezing, nasal discharge, conjunctivitis and painful corneal disease. Young kittens can be especially severely affected.

A branching corneal ulcer is strongly associated with herpesvirus, but eye disease cannot be safely assessed at home. Squinting, a cloudy eye or marked eye pain warrants prompt examination. [3]

Calicivirus often causes painful ulcers on the tongue or elsewhere in the mouth alongside mild upper-respiratory signs. Some strains are associated with temporary shifting lameness.

Rare severe systemic variants can cause widespread illness and high mortality in outbreaks. Marked swelling, jaundice, bleeding or rapid deterioration needs urgent veterinary assessment and infection-control advice. [4]

A blocked nose reduces smell, while fever, mouth ulcers, sore throat and nausea can make eating uncomfortable. Cats can become dehydrated and nutritionally compromised when poor intake continues.

Reduced appetite is therefore more than an inconvenience. A cat that is eating very little, cannot swallow comfortably or is becoming weak needs prompt veterinary contact, with kittens assessed especially quickly. [1]

Open-mouth breathing, marked effort to breathe, blue or grey gums, collapse or severe weakness is an emergency. Contact an emergency veterinary service immediately and explain that a contagious respiratory infection is possible.

Pneumonia, airway obstruction and other heart or lung disease can resemble severe cat flu. A cat in respiratory distress should be handled as little as possible and not subjected to forced food, water or steam. [4]

Herpesvirus can damage the cornea as well as cause conjunctivitis. A cat may squint, hold the eye closed, avoid light or develop a cloudy or visibly damaged surface.

Corneal ulcers are painful and can worsen without suitable treatment. Prompt examination allows staining of the eye, checks its depth and prevents inappropriate eye products from delaying healing. [3]

Many straightforward cases are recognised from the pattern of eye, nose and mouth signs, the cat's history and examination. The vet also assesses hydration, temperature, lungs, mouth and corneas.

Testing becomes more useful in severe, unusual, persistent or multi-cat disease. Diagnosis also considers foreign material, dental disease, polyps, fungal infection, tumours and other causes of chronic nasal signs. [1]

PCR can detect genetic material from specific respiratory organisms in eye, mouth or nasal samples. It can support outbreak investigation or an unusual clinical picture.

A negative result does not always exclude infection, and a positive result may occur in a healthy carrier or after some vaccines. Sampling site, timing and symptoms determine how useful the result is. [4]

Herpesvirus may not be detectable at every site or on every occasion because shedding can be intermittent. Combining conjunctival, throat and nasal samples can improve the chance of detection.

The result still needs clinical interpretation. Latent infection is common, so detecting viral DNA does not automatically prove that herpesvirus explains every current sign. [3]

No. Cat flu can leave chronic rhinitis, but persistent, bloody or one-sided discharge can also reflect dental disease, a foreign body, polyp, fungal infection or tumour.

A longer investigation may include imaging, dental assessment, sampling or rhinoscopy. Repeatedly assuming infection can delay diagnosis of a structural problem that needs different care. [1]

Treatment is mainly supportive: maintaining hydration and nutrition, easing discomfort, keeping the nose and eyes clear, and treating important eye or secondary bacterial disease. Severe cases may need hospital care.

The combination depends on the agent, corneal health, appetite and breathing. There is no single over-the-counter cure, and medicines safe for people may be dangerous to cats. [1]

No. Antibiotics do not treat herpesvirus or calicivirus, and uncomplicated viral disease may improve without them. They are considered when bacterial involvement is clinically important or complications develop.

Discharge colour alone does not identify the organism or select a drug. The vet weighs severity, duration, examination and previous treatment while avoiding unnecessary antimicrobial exposure. [5]

Veterinary antiviral treatment can help selected cats, especially those with significant herpesvirus eye disease. The route and medicine depend on whether disease affects the cornea, conjunctiva or wider respiratory tract.

Antivirals are not interchangeable, and some products used in people are unsafe or ineffective in cats. A vet needs to confirm the indication and monitor response. [3]

After veterinary assessment, a warm quiet space, clean eyes and nose, easy access to water and appealing food can support recovery. Gentle cleaning may improve comfort and smell.

Support must not become forced feeding, stressful restraint or exposure to irritating vapour. Poor intake, worsening eye pain, lethargy or breathing changes mean the cat needs reassessment rather than more home remedies. [2]

Hospital care may be needed when a cat cannot maintain hydration or nutrition, has pneumonia or breathing difficulty, needs intensive eye treatment, or is severely weak. These signs need urgent veterinary assessment, and kittens can deteriorate quickly.

In hospital, the team can provide controlled fluids, nutrition, oxygen and prescribed treatment while monitoring complications. Infection-control measures also protect other feline patients. [2]

Yes. Vaccination greatly reduces the likelihood of severe herpesvirus and calicivirus disease but does not prevent every infection or every sign. Different viral strains and exposure levels matter.

A vaccinated cat with respiratory signs still needs appropriate care and can still spread infection. The benefit is lower disease severity and fewer serious complications, not an absolute barrier. [4]

Often yes. Natural infection does not guarantee lasting protection against all calicivirus strains, and herpesvirus can remain latent rather than being eliminated. Vaccination can still reduce future disease.

Timing depends on recovery, prior vaccines, age and ongoing exposure. The veterinary team can build an individual plan once the cat is well enough rather than assuming previous illness provides complete immunity. [4]

Secretions can contaminate bowls, bedding, carriers, hands and surfaces. Removing organic material before using an agent-appropriate disinfectant reduces this indirect route of spread.

Calicivirus is harder to inactivate than enveloped herpesvirus, so not every household cleaner is suitable. Product instructions and veterinary infection-control advice matter, and cats must be protected from wet chemicals and fumes. [4]

A gradual introduction with separate resources initially allows health observation and reduces immediate close-contact exposure. Vaccination history and current signs are checked before mixing cats.

A symptom-free cat can still carry an organism, so one negative test is not a universal clearance certificate. Stable small groups, hygiene and low stress are more reliable than testing alone. [4]

Yes. Herpesvirus remains latent in the nervous system after the initial infection and can reactivate later. A flare may cause eye or respiratory signs, or virus may be shed without obvious illness.

Stress and other illness can contribute to recurrence, but not every sneeze is herpesvirus. Repeated eye pain or chronic nasal disease deserves reassessment for complications and other causes. [3]

A carrier has retained or continues to shed an infectious agent after the obvious illness. Herpesvirus typically becomes latent with intermittent shedding, while calicivirus can be shed more continuously.

Carrier status does not mean a cat is constantly ill or permanently unsafe to live with others. Risk management considers symptoms, household vulnerability, vaccination, hygiene and the uncertainty of shedding. [1]

Severe viral inflammation can permanently alter delicate nasal structures, leaving chronic rhinitis and greater susceptibility to secondary infection. Congestion and discharge may then wax and wane.

Long-term signs still need periodic review because dental disease, polyps, fungal infection and tumours can look similar. Management focuses on comfort and identified complications rather than assuming active virus every time. [1]

Most otherwise healthy adult cats recover from uncomplicated upper-respiratory disease, but kittens and vulnerable cats can become seriously ill. Eye damage, pneumonia, poor intake and severe systemic calicivirus worsen the outlook.

Recovery from the episode does not always remove the organism or prevent chronic signs. Follow-up focuses on comfortable breathing, eating, eye health and whether symptoms are truly resolving. [1]

Reassessment is needed when signs worsen, eating or drinking remains poor, an eye is painful, breathing changes, or improvement stalls. Persistent one-sided or bloody discharge also deserves investigation.

The original infection may have caused a complication, or the diagnosis may need broadening. Waiting through repeated courses of similar care can delay recognition of pneumonia, corneal disease or a structural nasal problem. [2]