Feline Viral Upper Respiratory Tract Disease

FHV-1 is a DNA virus that, while it does not mutate, remains in a dormant state following acute infection, and can become reactivated later in life in response to stress.88 FCV is a small single-stranded RNA virus that readily mutates during replication resulting in many different strains of the virus.

Disease Overview

Feline viral upper respiratory tract disease is typified by signs of rhinosinusitis, conjunctivitis, lacrimation, salivation, and/or oral ulcerations. The principal causative agents are feline herpesvirus type 1 (FHV-1) and feline calicivirus (FCV).


  • FCV is widespread in the general cat population, ranging from 10% for household pets kept in small groups up to 40% in some large colonies.
  • After FHV-1 infection, virtually all cats will remain latently infected, becoming lifelong carriers of the virus.



  • Hypersalivation
  • Oral ulcerations
  • Sneezing
  • Nasal discharge
  • Fever
  • Anorexia
  • Dyspnea
  • Depression


  • Conjunctivitis
  • Ocular ulceration
  • Ocular discharge
  • Sneezing
  • Nasal discharge
  • Salivation
  • Pharyngitis
  • Lethargy
  • Fever
  • Anorexia


  • Retching
  • Sneezing
  • Watery nasal discharge
  • Coughing
  • Pneumonia, inappetence, fever, and lethargy in severe cases



Occasionally signs of lameness due to acute arthritis (synovitis) will manifest. This usually only lasts a few days, and there will often be signs of respiratory disease at the same time.

Rarely, outbreaks of more severe strains have been manifested. Infection with these strains can result in severe pneumonia, hepatitis, pancreatitis, skin swelling and ulceration, and bleeding from the nose and intestine. In these outbreaks up to 50% of affected cats can die.


Acute upper respiratory tract disease is the most common manifestation of FHV infection.

A less common manifestation of chronic FHV infection is conjunctivitis and keratitis. FHV infection causes the development of multiple small branching corneal ulcers (called ‘dendritic keratitis’). Rarely, chronic FHV infection can result in skin inflammation and ulceration. This is most commonly seen around the nose and mouth but can affect other areas such as the front legs.


FCV is relatively resistant to environmental conditions and can potentially survive up to a month in the environment, although in most cases probably does not survive more than 7-14 days.

Viral excretion of FHV-1 may last for 1 to 3 weeks. After infection, virtually all cats will become lifelong carriers of the virus. Some of these cats will intermittently shed virus again, commonly following episodes of stress or immunosuppression.


In most cases, a specific diagnosis of FCV or FHV-1 infection will not be required. The presence of typical upper respiratory signs is enough for a presumptive diagnosis of FCV and/or FHV-1 infection. Signs of oral ulceration and milder respiratory signs tend to suggest the involvement of FCV whereas more severe respiratory illness and signs of keratitis in may suggest the involvement of FHV-1.

Merck Animal Health Vaccines


A quality core vaccine shown to be effective for vaccination of healthy cats 9 weeks of age or older against feline rhinotracheitis, calici, and panleukopenia viruses.

Professional Resources and Educational Materials

Keep your clinic and staff informed and aware of diseases and outbreaks.

Feline Sarcomas – What Do We Really Know


Summary of the latest information about feline sarcomas.


Feline Vaccination Guide


A guide to help your pet parents understand common feline diseases and the importance of customizing vaccination for their pet’s unique lifestyle.


Feline Leukemia Virus


Educate your clients about FeLV with this easy to share brochure.


No items to show.