Feline upper respiratory infection — often called a cat cold or cat flu — is one of the most common illnesses seen in cats of all ages. In shelters and multi-cat homes it spreads rapidly; even vaccinated cats are not completely immune. Understanding what causes URI, how to recognise it, when to call the vet and how to help your cat recover makes a stressful illness much more manageable.
What Is Feline Upper Respiratory Infection?
A feline upper respiratory infection (URI) is an infection of the nose, throat, sinuses and/or eyes caused by one or more viral or bacterial pathogens. About 90% of cases are caused by two viruses: feline herpesvirus type 1 (FHV-1) and feline calicivirus (FCV). Other contributors include Bordetella bronchiseptica, Chlamydophila felis and Mycoplasma species. FHV-1 is particularly significant because, like human herpes simplex virus, it establishes a lifelong latent infection that periodically reactivates during stress or immunosuppression.
Symptoms of Feline Upper Respiratory Infection
Symptoms typically appear two to five days after exposure and include sneezing (sometimes violent and frequent), nasal discharge ranging from clear and watery to thick yellow or green, eye discharge and conjunctivitis, nasal congestion sometimes causing open-mouth breathing, fever, lethargy, decreased grooming, loss of appetite (cats rely heavily on smell, and congestion kills their ability to smell food), and oral ulcers — particularly with calicivirus. FHV-1 tends to cause more severe eye involvement including corneal ulcers that can permanently scar the eye if untreated.
Diagnosis and When to See a Vet
Mild URI in a previously healthy adult cat can be managed at home for the first few days. Seek veterinary care promptly if the cat stops eating or drinking for more than 24–48 hours, has difficulty breathing or breathes with an open mouth, shows eye cloudiness or severe discharge, is running a high fever, is a kitten, senior cat or immunocompromised adult, or if symptoms worsen or do not improve within a week. Definitive viral identification via PCR testing is available for severe or recurrent cases.
Treatment of Feline URI
Mild URI treatment centres on supportive care: keep the cat warm and comfortable; clean eye and nose discharge gently with warm water or saline-soaked cotton pads several times daily; run a cool-mist humidifier or place the cat in a steamy bathroom for 10–15 minutes twice daily to loosen congestion; warm food or try strongly scented wet food to encourage eating; and consider L-lysine supplementation for FHV-1. For bacterial infections, antibiotics (doxycycline, azithromycin or amoxicillin-clavulanate) are prescribed. FHV-1-related eye disease may require topical antiviral eye drops or oral famciclovir.
Prevention: Vaccination and Environmental Management
The core FVRCP vaccine protects against feline rhinotracheitis (FHV-1), calicivirus and panleukopenia. Vaccination significantly reduces severity and the risk of chronic disease. In multi-cat homes, prevent URI spread by quarantining new cats for two weeks before introduction, using separate food bowls and litter boxes, washing hands between handling cats, and reducing stress through environmental enrichment and feline pheromone diffusers if needed. Shelter cats are at very high risk — early socialisation, prompt treatment of sick cats and good ventilation help control outbreaks.