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Feline Upper Respiratory Infection

Highly contagious respiratory infection in cats, primarily caused by feline herpesvirus (rhinotracheitis) and calicivirus (accounting for ~90% of cases). Often called "cat flu." Extremely common in shelter and multi-cat environments. Vaccination minimizes severity.

Key Facts

90% caused by herpesvirus and calicivirus; remainder by Chlamydophila, Bordetella, Mycoplasma
Signs: sneezing, nasal discharge, runny eyes, cough, oral ulcers, fever, hoarse voice
Herpesvirus: recurs with stress throughout life; contagious for ~2 weeks after episodes
Calicivirus: continuous shedding possible; some cats shed for life
Spread by sneezing, shared food bowls, toys, or human caretakers
Infection rate in some areas exceeds 60% — most shelter cats are likely infected
Most colds resolve in 7-10 days; kittens hit hardest
Hospitalization needed if: appetite loss, open-mouth breathing, high fever
Treatment: antibiotics for secondary infections, antivirals (famciclovir) for severe herpes
Vaccination (FVRCP): core vaccine; minimizes severity but may not prevent infection
Available as injectable or intranasal; nasal provides faster protection (3-4 days)
Hemorrhagic calicivirus: rare but rapidly fatal virulent strain