Feline upper respiratory infection (URI)

Symptoms an owner can spot at home

• Sneezing, congestion, or nasal discharge
• Ocular discharge, squinting, or conjunctivitis
• Ulcers on the tongue, gums, or nose (especially with calicivirus)
• Reduced appetite (often due to nasal congestion blocking smell)
• Mild fever and lethargy

When to see a vet

• Any URI signs in a kitten under 12 weeks, dehydration and hypoglycemia are the main risks
• Refusal to eat for more than 24 hours in any cat, hepatic lipidosis develops quickly in cats with even short fasts, especially overweight ones
• Difficulty breathing, open-mouth breathing, or blue gums, urgent care
• Cloudy eye, deep ulcer, or squinting, corneal complications from herpesvirus can threaten vision

What it is

Feline URI is a syndrome, most commonly caused by feline herpesvirus-1 (FHV-1) and feline calicivirus (FCV), with Bordetella bronchiseptica, Chlamydia felis, and Mycoplasma as secondary or primary bacterial contributors. Transmission is by direct contact and fomites; the crowded shelter or foster environment is the classic setting.

FHV-1 establishes lifelong latent infection; cats can shed the virus intermittently during stress (boarding, new pet, moving) even years after the initial infection. FCV is more genetically variable; a severe virulent systemic strain (VS-FCV) has been reported in outbreaks and carries a much higher mortality rate. Vaccination reduces severity, not necessarily infection.

Treatment overview

This is editorial overview, not a treatment plan. Supportive care is the mainstay, humidification (steamy bathroom), gentle nose wiping, warm palatable food to encourage eating, and hydration. Antibiotic class is used when there is evidence of bacterial infection (purulent discharge, fever, non-resolving course), not prophylactically. Antiviral class (famciclovir, topical cidofovir) is used for severe or ocular herpesvirus. L-lysine supplementation was historically recommended but recent evidence does not support routine use.

What owners can do

• Keep core FVRCP vaccination current (protects against FHV-1, FCV, and panleukopenia).
• Quarantine new cats for 2 weeks before introducing to the resident cat.
• Minimize stress (routine, resources, hiding spots) to reduce herpesvirus reactivation.
• Handle sick cats last and wash hands and change clothes before touching healthy cats.