Upper respiratory infection (URI) is the most common infectious illness in cats, responsible for the majority of sneezing, runny nose, and eye discharge cases. Most URIs are caused by herpesvirus (FHV-1) or calicivirus — both vaccine-preventable. While most adult cats recover in 1–2 weeks, kittens, seniors, and immunocompromised cats can deteriorate quickly.
Last reviewed: June 2026
What Causes Upper Respiratory Infection in Cats?
Feline upper respiratory infection is caused most often by feline herpesvirus type 1 (FHV-1) and feline calicivirus (FCV), which together account for approximately 80–90% of feline URI cases, as described in Helps et al., 2005, JFMS. Other contributing pathogens include Chlamydophila felis (which causes particularly prominent conjunctivitis) and Bordetella bronchiseptica. Mycoplasma species are increasingly recognized as co-infecting agents. Once infected with FHV-1, cats become lifelong carriers — stress, illness, or corticosteroid treatment can trigger viral recrudescence months or years later. The AAFP-AAHA Feline Life Stage Guidelines, 2021 recommend FHV-1 and FCV vaccination as core vaccines for all cats, starting at 6–8 weeks and maintained with appropriate boosters.
Signs of Cat URI
URI signs range from mild sneezing to severe systemic illness depending on the pathogen, viral load, and the cat's immune status:
- Sneezing — often repetitive, sometimes forceful with discharge
- Nasal discharge: clear (early viral), thick yellow-green (secondary bacterial infection)
- Eye discharge: watery or mucoid; conjunctivitis (red, swollen conjunctiva)
- Squinting or pawing at the eyes (ocular pain, common with FHV-1 corneal ulcers)
- Fever, lethargy, and reduced appetite
- Mouth ulcers, drooling, tongue lesions — more typical of calicivirus
- Labored or open-mouth breathing if congestion is severe
Kittens under 8 weeks with URI are high-risk for rapid deterioration, anorexia-related hypoglycemia, and pneumonia. Any kitten that stops nursing or eating requires same-day assessment.
When URI Needs More Than Rest
Most healthy adult cats with mild URI — sneezing and runny eyes but still eating and alert — can be supported at home with warm food (smell encourages eating), gentle cleaning of discharge, and a humidifier. However, several situations require veterinary care:
Bacterial secondary infections are common after viral URI and require antibiotics. FHV-1 corneal ulcers (dendritic ulcers) require topical antiviral drops (idoxuridine, cidofovir) to prevent corneal scarring. A cat that stops eating for more than 24–48 hours risks hepatic lipidosis and needs assisted nutritional support.
When to See a Vet
Call your vet today if:
- Your cat has not eaten for 24 hours or more despite the URI
- Eye discharge is thick, yellow-green, or your cat is squinting persistently
- Nasal discharge has become thick and colored (not clear)
- Your kitten is sneezing and not feeding normally
Go to the ER immediately if:
- Your cat is breathing with its mouth open or gasping
- Gums appear pale, white, or bluish
- Your kitten is limp, unresponsive, or extremely cold
- Your cat has not eaten or drunk for 48+ hours
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Frequently Asked Questions
How long does cat URI typically last?
Uncomplicated viral URI in a healthy adult cat typically resolves in 7–14 days with supportive care. Cats with secondary bacterial infections may take 3–4 weeks. Cats with FHV-1 may have recurring episodes throughout life, particularly during stress. Persistent or worsening signs beyond 2 weeks always warrant a vet visit.
Is my cat's URI contagious to other cats?
Yes — FHV-1 and calicivirus spread easily between cats via direct contact, shared food bowls, and airborne droplets. Isolate any URI cat from healthy housemates, use separate food and water bowls, and wash hands between handling cats. Disinfect surfaces with dilute bleach or veterinary disinfectants; FHV-1 is killed by common household disinfectants.
What does cat URI treatment cost?
An office visit to diagnose URI and prescribe treatment typically costs $60–150. Antibiotics for secondary bacterial infection run $30–60 for a 10–14 day course. Topical ocular antivirals cost $40–100. If hospitalization is needed (a kitten not eating, a cat with pneumonia), expect $400–1,200 for 1–2 days. Vaccination prevention costs far less.
Can I use human cold remedies for my cat with URI?
Never. Human cold and flu medications — particularly those containing acetaminophen, pseudoephedrine, or xylitol — are toxic to cats. Even small doses of acetaminophen can be fatal. Only use medications specifically prescribed or approved by your veterinarian.
Does the herpesvirus stay in my cat forever?
Yes. FHV-1 establishes lifelong latency in the trigeminal ganglion after primary infection. Most cats remain asymptomatic between flares, but stress — boarding, new pets, illness, or owner absence — can trigger recrudescence with sneezing and eye discharge. L-lysine supplementation has traditionally been recommended, though current evidence for its efficacy is mixed.
Still Not Sure if Your Cat Needs a Vet?
When you're not sure if this is wait-and-see or call-tonight, Voyage AI Vet triages in under 2 minutes. Describe what you're seeing in chat, share photos of any eye or nasal discharge, or a short clip of your cat's breathing pattern, or hop on a live video call if you want a second pair of eyes. Every answer comes with citations to the actual veterinary literature it's pulling from — so you see exactly where the guidance comes from, not just a chatbot's word.