Feline viral rhinotracheitis (FVR) is an upper respiratory infection of cats caused by feline herpesvirus 1, of the family Herpesviridae. It is also known as feline influenza and feline coryza. Viral respiratory diseases in cats can be serious, especially in catteries and kennels. Causing one-half of the respiratory diseases in cats, FVR is the most important of these diseases and is found worldwide. The other important cause of feline respiratory disease is feline calicivirus.