FHV-1 (Feline Herpesvirus 1), a cat’s type 1 herpesvirus is the key pathogen causing upper respiratory tract diseases in cats (URTD). The herpesvirus infection can progress differently. Without complications, the disease lasts from 10 to 14 days; unfortunately, secondary infections are frequent. The classical form of the disease manifests itself in sneezing, nasal secretion, transient fever and conjunctival hyperaemia. Possible symptoms include photophobia, swollen eyelids and lack of appetite. Sometimes, excessive salivation and coughing can occur. In the acute disease, tracheitis, bronchitis and pneumonia can occur. The herpesvirus infection can also be chronic. Relapses can be dangerous to a cat, in particular, persistent conjunctivitis and corneal swelling which can lead to blindness. Infections with FHV-1 occur by a direct contact with the saliva or other effusions of a sick cat or using common bowls. Moreover, the virus can pass from a sick queen cat to kittens. Most often, cats in larger clowders fall ill.