Feline Upper Respiratory Infection (Cat Flu)
Extremely common in cats, especially in shelters and multi-cat environments. Most often caused by feline herpesvirus (FHV-1) and calicivirus (FCV). Similar to the common cold in humans but can be serious in kittens and immunocompromised cats.
Last updated: 2026-05-10
Severity
mild
When to Act
See Vet Soon
Symptoms & Signs
Sneezing
Paroxysmal sneezing fits, often producing clear or colored discharge.
Nasal and eye discharge
Clear initially, may become thick yellow/green with secondary bacterial infection.
Conjunctivitis
Red, swollen eyes; squinting; ocular discharge. Especially prominent with herpesvirus.
Fever and lethargy
Especially in the first few days of infection.
Oral ulcers
Painful ulcers on the tongue, gums, or palate — classic for calicivirus.
Decreased appetite
Cats with congested noses cannot smell food and may stop eating.
Behavioral Changes to Watch For
Pets can't tell us what's wrong. These behavioral changes are often the first clues that something is wrong.
🐾 Not eating despite interest
Cat approaches food but walks away — they can't smell it due to nasal congestion.
What You May Notice:
Your cat sniffs the food bowl intently but seems unable to find the food, then gives up frustrated.
Causes & Risk Factors
Causes
- •Feline herpesvirus type 1 (FHV-1) — most common; causes lifelong latent infection with periodic reactivation under stress
- •Feline calicivirus (FCV) — second most common; causes oral ulcers and limping syndrome
- •Chlamydia felis — primarily ocular disease (conjunctivitis)
- •Bordetella bronchiseptica — less common in cats but possible
- •Co-infections are common — especially in shelter populations
Risk Factors
- ⚠Shelters, catteries, multi-cat households
- ⚠Kittens (immature immune system)
- ⚠Stress — adoption, moving, boarding, new pet, owner vacation
- ⚠Unvaccinated cats
- ⚠Brachycephalic breeds (Persians, Himalayans) — more severe respiratory signs
How It's Diagnosed
- 1Clinical signs — usually diagnostic in the right context (sneezing + conjunctivitis in a shelter kitten)
- 2PCR panel for specific pathogens (herpesvirus, calicivirus, Chlamydia, Mycoplasma, Bordetella)
- 3Chest radiographs if pneumonia suspected
- 4Response to treatment supports diagnosis
Treatment Options
Supportive Home Care
Most cases are self-limiting and resolve with excellent supportive care.
Steps
- 1.Warm, humidified environment — steamy bathroom 10-15 min, 3x daily
- 2.Gently clean nasal and eye discharge with warm, damp cloth
- 3.Warm up food slightly to enhance aroma — cats MUST eat
- 4.Syringe feeding with recovery diet if not eating voluntarily
- 5.L-lysine supplementation (controversial — recent evidence questions efficacy for herpesvirus)
Expected Outcome
Most cats recover in 7-14 days with supportive care.
Precautions
- !Anorexic cats can develop hepatic lipidosis within 48-72 hours
- !If the cat cannot smell, they will not eat — appetite stimulants may help
Antibiotics and Antivirals
For secondary bacterial infections or severe herpesvirus cases.
Steps
- 1.Doxycycline — first choice when antibiotics are indicated (covers Chlamydia, Mycoplasma, Bordetella)
- 2.Famciclovir — oral antiviral for severe or recurrent herpesvirus keratitis/respiratory disease
- 3.Cidofovir or idoxuridine ophthalmic — topical antiviral for herpesvirus ocular disease
- 4.Antibiotics are not always needed — many cases are primarily viral
Expected Outcome
Faster resolution of secondary bacterial components and reduced herpesvirus shedding.
Precautions
- !Famciclovir is expensive and requires frequent dosing (2-3x daily)
- !Systemic antiviral resistance is possible with long-term use
Common Medications Used
| Medication | Usage | Important Notes |
|---|---|---|
| Doxycycline | Antibiotic for secondary bacterial infections | Covers Chlamydia and Mycoplasma. Give with food/water. |
| Famciclovir | Antiviral for severe feline herpesvirus infections | Used for severe or chronic herpesvirus cases. Metabolized to penciclovir in cats. |
Prevention
- ✓Core FVRCP vaccination — reduces severity of disease (does not prevent infection)
- ✓Reduce stress — consistent routine, environmental enrichment
- ✓Isolate sick cats from healthy cats
- ✓Quarantine new cats for 2 weeks
- ✓Good ventilation and hygiene in multi-cat environments
When to See a Veterinarian
- ⚠️Cat stops eating for more than 24 hours
- ⚠️Thick yellow/green discharge (possible secondary bacterial infection)
- ⚠️Open-mouth breathing — EMERGENCY
- ⚠️Kitten with URI — more vulnerable, seek care early
Frequently Asked Questions
Can I catch a cold from my cat?
Prognosis
Excellent for most cats — self-limiting in 1-2 weeks. Herpesvirus carriers will have periodic flare-ups throughout life, often triggered by stress. Calicivirus carriers shed the virus for weeks to months but most eventually clear it.
References
- [1] AAFP — Feline Respiratory Disease Guidelines
- [2] ISFM — Shelter Medicine Guidelines
Related Conditions
Feline Asthma (Allergic Bronchitis)
A chronic inflammatory respiratory condition similar to human asthma. Affects 1-5% of cats. Causes coughing, wheezing, and difficulty breathing. Manageable with proper treatment.
moderateHeartworm-Associated Respiratory Disease (HARD) in Cats
Cats are atypical hosts for heartworm, but even a single worm can cause severe, potentially fatal respiratory disease. Prevention is essential — there is no approved adulticide treatment for cats.
severeKennel Cough (Infectious Tracheobronchitis)
A highly contagious respiratory infection causing a characteristic dry, hacking cough. Often compared to the common cold in humans. Usually self-limiting but can progress to pneumonia in vulnerable dogs.
mildFeline Lower Urinary Tract Disease (FLUTD)
A common and potentially life-threatening syndrome in cats involving inflammation of the bladder and urethra. Can cause urinary blockage in male cats, which is a medical emergency.
severe