“Cat flu” (or kitten flu) is a general term used to describe upper respiratory tract infections in cats. It is highly contagious and the signs can be particularly serious in kittens. It is typically transmitted by direct or close contact between kittens or cats, e.g., in sneezed droplets. 

Despite the name, cat flu is not actually caused by a feline influenza virus (or feline flu virus). There are several infectious organisms that can be involved, but it is mainly caused by two viruses, feline herpesvirus (also known as feline rhinotracheitis virus) and feline calicivirus. 

Cat flu signs and symptoms in kittens can be particularly serious due to their immature immune systems. In some cases it may look like a kitten “cold” (e.g., a kitten with a snotty nose) but in other cases the signs can be much more serious. The signs can vary depending on which infectious organism is involved.

Symptoms of cat flu may include:
•    Sneezing and/or coughing
•    Discharge from the eyes
•    Discharge from the nose
•    Mouth ulcers causing drooling
•    Low energy levels
•    Decreased appetite
•    Fever 
•    Difficulty breathing
•    Joint pain, stiffness, and limping

If a kitten or cat is infected with feline herpesvirus, the virus can persist in their bodies and they may experience ongoing signs or recurrent flare ups of cat flu.