Indoor cats get colds primarily through three routes: viruses carried into the home on your hands and clothing, dormant infections that reactivate under stress, and exposure to other pets in the household. Even a cat that never steps outside is not sealed off from the pathogens that cause feline upper respiratory infections.
What Causes Cat Colds
Two viruses are responsible for the vast majority of feline respiratory infections. Feline calicivirus accounts for roughly half of all cases, and feline herpesvirus covers most of the rest. Sometimes both strike at once. Bacterial species can also cause respiratory illness on their own or pile on top of a viral infection, making symptoms worse and harder to resolve.
These are not human cold viruses. You can’t give your cat a cold, and your cat can’t give you one. Feline respiratory pathogens are species-specific, which is why the ways they reach an indoor cat can seem so puzzling.
You Can Bring It Home
The most common way an indoor cat encounters a respiratory virus is through you. Feline calicivirus spreads through saliva, nasal mucus, and eye discharge from infected cats, and it can hitch a ride on hands, clothing, shoes, and any surface that has contacted a sick or carrier cat. If you pet a neighbor’s cat, visit a shelter, or even handle items that were near an infected animal, you can transport the virus into your home without knowing it.
Calicivirus is particularly stubborn. It persists on surfaces in the environment long enough that contaminated clothing or equipment can serve as a bridge between cats that never physically meet. Feline herpesvirus is more fragile outside a host, surviving only hours on dry surfaces, but it can still travel on freshly contaminated hands or fabrics. The practical takeaway: washing your hands before handling your cat after contact with other cats is a simple and effective precaution.
Dormant Viruses That Wake Up
This is the route that surprises most cat owners. After a cat recovers from feline herpesvirus, the virus doesn’t leave the body. It hides in nerve cells, establishing a lifelong latent infection. Almost all cats that have been infected go through this. During latency the cat appears perfectly healthy and doesn’t shed the virus to other animals.
But stress can flip the switch. A move to a new home, a change in routine, the arrival of a new pet, loud construction, or even a visit to the vet can trigger reactivation. When the virus wakes up, the cat starts shedding it again and may develop familiar cold symptoms: sneezing, watery eyes, congestion. Sometimes reactivation is mild enough that the cat shows no outward signs at all but is still contagious to other cats in the home.
This means a cat adopted years ago, one that seemed perfectly healthy at the time, can suddenly develop a “cold” with no apparent source. The source was already inside the cat. Nursing mothers can even pass the virus to kittens this way, because the stress of birth and lactation is enough to trigger reactivation and shedding.
Other Pets in the Household
If you have more than one cat, transmission is straightforward. Infected cats shed virus through sneezing, grooming, and sharing food or water bowls. Aerosol droplets from a single sneeze can carry calicivirus across a room. The incubation period for calicivirus ranges from 2 to 14 days, so by the time the first cat shows symptoms, the second cat may already be infected.
Dogs can also be a factor. The bacterium Bordetella bronchiseptica, best known for causing kennel cough in dogs, can infect cats as well. A dog that visits a boarding facility, dog park, or groomer could bring this pathogen home and pass it to a cat that never leaves the house.
How to Tell Your Cat Has a Cold
The signs look a lot like a human cold. Sneezing, runny nose, watery or goopy eyes, and mild lethargy are the most common. Some cats lose their appetite because congestion dulls their sense of smell, and cats rely heavily on smell to find food appealing. Calicivirus often causes ulcers on the tongue or roof of the mouth, which can make eating painful.
Most mild cases clear up within 7 to 10 days. But bacterial complications can drag things out. Opportunistic bacteria tend to invade the lower respiratory tract when a virus has already damaged the protective lining of the airways. If your cat develops a thick, colored nasal discharge, starts breathing with its mouth open, or stops eating entirely, the infection may have progressed beyond a simple cold.
Reducing the Risk for Indoor Cats
Vaccination is the single biggest protective measure. Core feline vaccines cover both calicivirus and herpesvirus. They don’t guarantee a cat will never get infected, but they significantly reduce the severity of illness.
Beyond vaccination, a few practical habits make a difference. Wash your hands after handling unfamiliar cats before touching your own. If you volunteer at a shelter or frequently interact with stray cats, changing your outer layer of clothing before greeting your cat at home reduces the chance of carrying a virus inside. Keep food and water bowls separate in multi-cat households, and clean them daily.
For cats that carry a latent herpesvirus infection, minimizing stress is a form of prevention. Predictable routines, gradual introductions to new pets or environments, and quiet spaces where the cat can retreat all help keep the immune system from tipping the balance toward reactivation.