Cat Upper Respiratory Infection: Symptoms, Care, and When to Worry

Most "cat colds" are one of two viruses: feline herpesvirus (FHV-1) and feline calicivirus (FCV). Both are extremely common, both are contagious between cats, and both usually run their course in one to three weeks with supportive care. The reason they matter is not the sneezing. It is the blocked nose that stops a cat from smelling food, the eye that becomes an ulcer, and the kitten or senior cat who stops eating and dehydrates. Knowing which of those you are looking at is most of the job.

What actually causes it

FHV-1 and FCV account for the large majority of cases. Chlamydia felis and Mycoplasma species cause some, usually with more prominent eye signs, and Bordetella bronchiseptica occasionally contributes. Spread is by direct contact, sneeze droplets, and shared bowls, bedding, and hands. Incubation is roughly two to ten days. Cats that recover from herpes remain carriers for life and can shed virus again during stress, illness, or corticosteroid treatment, which is why some cats seem to get "colds" every time something changes at home.

Symptoms, and how the two viruses differ

Both cause sneezing, clear then cloudy nasal discharge, conjunctivitis, squinting, watery eyes, mild fever, and reduced appetite. Herpes tends to bring more eye involvement — corneal ulcers, sometimes a clouded or painful eye — and recurrent episodes. Calicivirus more often causes ulcers on the tongue, gums, or hard palate, drooling, and occasionally lameness. Neither virus responds to antibiotics; antibiotics are used only when a secondary bacterial infection is suspected, which usually shows as thick yellow-green discharge that persists or worsens after the first week.

The timeline you should expect

Days one to three: sneezing, clear discharge, watery eyes, slightly quieter cat but still eating. Days four to seven: discharge thickens, nose gets crusty, appetite may dip because the cat cannot smell. Days seven to fourteen: most cats improve steadily. Beyond two weeks without improvement, or any worsening at any point, means a re-check rather than continued waiting. Kittens, senior cats, and cats with feline leukaemia or immunodeficiency virus can become severely ill and should be seen early rather than observed.

Why they stop eating, and why that is the real risk

Cats rely on smell far more than taste. A blocked nose is not a minor inconvenience; it removes the trigger for appetite, and a cat that cannot smell food will often sit in front of the bowl and walk away. Add a sore throat or mouth ulcers and the cat has two reasons to refuse. This is where a routine cold becomes dangerous: 24 to 48 hours without food in a cat, especially an overweight one, raises the risk of hepatic lipidosis. Treat appetite as a vital sign, not a preference.

Home care that genuinely helps

Clear the nose before meals: warm saline on a cotton pad, wiped gently, then a few minutes in a steamy bathroom (run the shower hot, sit with the cat outside the water). Saline nasal drops designed for infants or pets can soften crusts. Warm the food to body temperature and offer strong-smelling wet food, sardine water, or a recovery diet; hand-feeding and flat plates help. Wipe eye discharge with separate damp pads, one per eye, and never reuse. Keep the cat warm, quiet, and separate from other cats, and wash your hands and bowls between cats. A humidifier in a small room is reasonable; avoid essential oil diffusers entirely, as many are toxic to cats.

Home care that does not help

Lysine supplements have been recommended for years, but the evidence for reducing herpes outbreaks is weak and some studies suggest harm at high doses; do not rely on it. Do not use human cold remedies, decongestants, or leftover antibiotics. Do not put human eye drops in a cat's eye, and do not use steroid eye drops on a squinting cat — with herpes, steroids can worsen a corneal ulcer. Do not let a cat with eye signs go untreated because "it is just a cold"; a melting ulcer can perforate the eye within days. Skip dairy, and skip forcing food into a cat who cannot smell it.

When to see a vet the same day

• No food for 24 hours, or any food refusal in a kitten.
• One eye held closed, cloudy, or visibly painful, or the eye looks different from the other.
• Breathing with the mouth open, or noisy, laboured breathing.
• Thick yellow-green nasal discharge with lethargy or fever.
• Ulcers, drooling, or refusal to swallow.
• Kitten, senior, or FIV/FeLV-positive cat with any of the above.
• No improvement after seven days, or worsening at any stage.

Recovery, carriers, and prevention

Supportive care plus time resolves most cases. Cats who have had herpes remain carriers, so recurrent mild episodes are expected and are managed the same way. Keep vaccinations current — they reduce severity rather than preventing infection entirely. In multi-cat homes, isolate the affected cat, use separate bowls and litter scoops, and wash hands. Reducing stress matters more than most owners expect, because stress is the main trigger for herpes reactivation. If your cat has repeated episodes, ask your vet about a management plan rather than treating each one from scratch. More on routine care and hygiene is in care, and general feline health background in health.

This is general information, not a diagnosis.

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