Feline Upper Respiratory Infection Complex (primarily FHV-1 and FCV)
Also known as: Cat Flu, URI
⚠ Emergency Warning Signs
Difficulty breathing, complete loss of appetite for more than a day (especially concerning in kittens), or severe lethargy/dehydration warrant prompt veterinary attention rather than home management.
Overview
Feline upper respiratory infection ('cat flu') is usually caused by feline herpesvirus-1 (FHV-1) and/or feline calicivirus (FCV), often in combination with secondary bacterial infection. It's extremely common, especially in kittens, shelters, and multi-cat environments, and is part of why these two viruses are covered by the core FVRCP vaccine. Most cases are manageable, but severe cases — especially in young kittens — can be serious.
Symptoms
- Sneezing
- Nasal and eye discharge
- Oral ulcers
- Reduced appetite
- Difficulty breathing (severe cases)
Causes
Most commonly feline herpesvirus-1 (FHV-1) and/or feline calicivirus (FCV), frequently with secondary bacterial infection (e.g., Bordetella, Chlamydophila) contributing to the overall illness. Feline upper respiratory infection complex most commonly involves feline herpesvirus and calicivirus, either alone or together, with bacterial secondary infection sometimes complicating the picture — genuinely one of the most common infectious conditions in cats, particularly prevalent in shelter and multi-cat environments where these highly contagious viruses spread easily.
Risk Factors
Kittens, unvaccinated cats, and cats in shelter, cattery, or other multi-cat environments are at the highest risk; stress and concurrent illness can trigger reactivation of latent herpesvirus in previously infected cats.
Transmission
Highly contagious via direct contact, sneezed respiratory droplets, and contaminated shared objects (bowls, bedding); FCV in particular can also survive in the environment for a meaningful period.
Incubation Period
Typically 2-10 days depending on the specific virus involved.
Disease Stages & Progression
Starts with sneezing and nasal/eye discharge, potentially progressing to more significant congestion, oral ulcers (particularly characteristic of calicivirus), reduced appetite (partly from reduced smell affecting interest in food), and in severe kitten cases, pneumonia or dangerous dehydration/weight loss.
Early Warning Signs
Sneezing, watery eyes, and mild nasal discharge — often the very first signs owners notice.
Advanced Symptoms
Thicker nasal/eye discharge, conjunctivitis (see that disease page for overlap), oral ulcers (especially with calicivirus, sometimes causing drooling and reduced interest in eating due to mouth pain), fever, lethargy, and in severe cases, difficulty breathing or pneumonia.
Diagnostic Methods
Usually a clinical diagnosis based on characteristic signs; PCR testing of eye/nasal/oral swabs can identify the specific virus(es) involved in recurrent, severe, or diagnostically unclear cases.
Veterinary Examination Process
Assessment of nasal and eye discharge, oral cavity for ulcers, chest sounds, hydration, and overall condition — particularly important in kittens given their lower reserve.
Recommended Lab Tests
PCR swab testing in select cases; otherwise largely a clinical diagnosis.
Diagnostic Imaging
Not typically needed for straightforward cases; chest X-rays if pneumonia is suspected in a severely affected cat.
Blood Test Indicators
Not typically diagnostic on their own for a straightforward case.
Biopsy / Histopathology
Not applicable.
Differential Diagnoses
Feline asthma (for respiratory signs specifically), other causes of eye/nasal discharge, and dental disease (for oral ulcers/drooling) — the combination of signs and, if needed, PCR testing help distinguish these.
Home Monitoring Guidance
Gently wiping away nasal/eye discharge, encouraging eating (warming food slightly can help since reduced smell affects appetite), and ensuring adequate water intake; monitoring closely for any worsening, especially in a kitten.
Veterinary Treatment Options
Supportive care for most cases: keeping the nose/eyes clean, encouraging eating, and ensuring hydration; antiviral medication or antibiotics (for secondary bacterial infection) as needed for more significant cases; severe cases, especially dehydrated or non-eating kittens, may need hospitalization for supportive care including fluids and assisted feeding. Supportive care (fluids, nutritional support, keeping nasal passages clear) forms the core treatment for most cases, which are viral and don't respond to antibiotics directly; antibiotics are added when secondary bacterial infection is suspected, and antiviral medication may be used for more severe or refractory herpesvirus-associated cases specifically.
Surgery Requirements
Not applicable for typical cases.
Recovery Timeline
Most cases resolve within 1-2 weeks with supportive care; cats infected with herpesvirus specifically may have intermittent recurrences throughout life during periods of stress, since the virus isn't cleared from the body (see the Conjunctivitis disease page for more on this pattern).
Possible Complications
Chronic or recurring signs (particularly with herpesvirus), secondary bacterial pneumonia in severe cases, chronic nasal or sinus changes from severe or repeated infections, and dangerous dehydration/weight loss in kittens who stop eating.
Long-Term Management
For cats with recurrent herpesvirus-related flares, stress reduction where possible; otherwise not typically needed once a straightforward case resolves.
Prevention
Vaccination (the FVRCP core vaccine covers both FHV-1 and FCV) reduces severity significantly, though doesn't guarantee complete prevention; good hygiene and reduced crowding in multi-cat environments reduce transmission.
Vaccination Availability
Core FVRCP vaccine, strongly recommended for all cats — see the Vaccination Center.
Prognosis
Good for most cases with supportive care; more guarded for severely affected, very young, or immunocompromised cats, and herpesvirus-related recurrence is a lifelong possibility for infected cats.
References
American Association of Feline Practitioners (AAFP); International Society of Feline Medicine (ISFM) upper respiratory disease guidelines.
Medications Used
- Antiviral medication (e.g., famciclovir) for significant herpesvirus-related disease
- Antibiotics for secondary bacterial infection
- Eye medication if conjunctivitis/corneal involvement is present
- Appetite stimulants or assisted feeding if needed
Estimated Treatment Cost by Country
| Country | Estimated Cost Range | Notes |
|---|---|---|
| IN | 800–4,000 INR | |
| US | 100–500 USD | |
| UK | 80–350 GBP | |
| AU | 120–600 AUD | |
| JP | 6,000–30,000 JPY | |
| DE | 80–350 EUR | |
| BR | 180–900 BRL |
Frequently Asked Questions
Is this the same as the common cold in humans?
It's a similar general concept (a viral upper respiratory illness) but caused by entirely different, species-specific viruses — you can't catch this from your cat, and your cat can't catch human colds from you.
Why does my cat keep getting sick with this?
If herpesvirus is the cause, recurrence is expected — the virus stays latent in the body long-term and can reactivate during stress, similar to how the related conjunctivitis condition behaves (see that disease page).
My kitten won't eat because of this — how worried should I be?
Genuinely worried enough to act promptly — kittens have much less metabolic reserve than adult cats, and not eating for even a day or two is a real risk on top of the respiratory illness itself; contact your vet rather than waiting it out.
Are the mouth ulcers serious?
They're uncomfortable and can significantly reduce a cat's interest in eating (which is the main practical concern), particularly associated with calicivirus — your vet can offer pain relief and encourage nutrition support if this is affecting your cat significantly.
Does vaccination mean my cat can never get this?
No vaccine is 100% protective, but vaccinated cats that do get infected typically have much milder illness — this is one of the clearest illustrations of why the core vaccines matter even for indoor cats.