Feline calicivirus and herpesvirus cause the most common upper respiratory infections in cats. Managing these conditions well protects welfare and reduces transmission.
Upper respiratory infections cause significant discomfort through nasal congestion that prevents cats smelling food, eye discharge, painful oral ulcers in calicivirus cases, and systemic illness. Cats whose nasal passages are completely blocked cannot smell their food and stop eating, creating a risk of hepatic lipidosis. Conjunctivitis causes painful eye irritation. Herpesvirus-associated corneal ulceration can be sight-threatening. Shelter cats are disproportionately affected due to stress-induced reactivation of herpesvirus and the transmission opportunities created by high density housing. Stress reduction, supportive care, and lysine supplementation for herpesvirus management address welfare during infection.