Cat flu is the common name for a feline upper respiratory disease, which can be caused by one or more possible pathogens:

1. Feline herpes virus, causing feline viral rhinotracheitis (cat common cold; this is the disease most associated with the "cat flu" misnomer),
2. Feline calicivirus,
3. Bordetella bronchiseptica (cat kennel cough), or
4. Chlamydia felis (chlamydia).

Cat flu is spread much the same way as "human flu": direct contact with others who are infected, generally through saliva, tears, or discharge from the eyes or nose. There is also the possibility of indirect spreading though contamination of food bowls, bedding, litter, or human hands. Even after recovery, many cats will remain carriers of the virus and have the potential to spread it to other cats.

To reduce the spread, veterinarians recommend vaccination of kittens.^[1] Already-infected cats must usually be isolated from all other cats for at least two weeks, and all objects touched by the cat must usually be decontaminated afterwards, including litter boxes, food bowls, and human hands.

Cat flu is typically diagnosed by a professional recognizing the common symptoms. Despite the variety of pathogens that may be responsible, some symptoms are generally considered to be shared,^{[by whom?]} including sneezing, nasal congestion, conjunctivitis, and discharge from the nose or eyes.^[2] More rare symptoms, meanwhile, include: a loss of appetite, lethargy, fever, enlarged lymph nodes, and blepharospasm (squinting).

In extreme cases where symptoms do not subside, veterinarians may run additional tests including chest x-rays, blood tests, or bacterial cultures.

Cat flu is typically treated at home and generally focuses on the animal's symptoms. Currently, there are no antiviral drugs to treat cat flu, but antibacterial (antibiotic) drugs can be prescribed if symptoms are long-lasting or severe. Veterinarians may also prescribe eye drops or pain medication to aid the healing process.

Other common home remedies include exposing the cat to warm, humid air (such as through a humidifier); gentle face washing to remove nasal discharge; and feeding the cat strong-smelling foods (due to the respiratory infections often impacting a cat's sense of smell, and by extension its appetite).^[3]

If a cat is suffering from excessive lethargy or dehydration, veterinarians may recommend hospital stays and, in extreme cases, appetite stimulants or the use of intravenous catheters or feeding tubes.

In South Africa, the term cat flu is also used to refer to canine parvovirus; however, that illness primarily affects dogs, though at times also mammals such as cats, skunks, and foxes.^[4]

In the 2013 psychological horror film Escape from Tomorrow, there is a fictional strain of cat flu surrounding the Disneyland parks, which a Disneyland nurse claims one "could be a host [of] and not even know it". The main protagonist Jim later experiences these symptoms in the end of the film, such as constipation, vomiting up massive hairballs and blood, and gradual weakening of his body, before his wife discovers his corpse the next morning with cat eyes and a grinning face.