• Note changes in your cat's appearance, as this may indicate cat flu.cat image by Appelez-moi Denyse from Fotolia.com
  
  Typically caused by two viral infections called feline herpes virus type 1 (FHV-1) and feline calicivirus (FCV), upper respiratory disease or "cat flu" is a common illness in cats. While there aren't any treatments that cure the flu itself, owners can take measures to alleviate symptoms, according to Pawprints and Purrs, an organization committed to cat well-being. It's important to recognize the range of cat flu symptoms as early as possible and to promptly seek veterinarian attention to effectively treat the disease and prevent rare complications such as death.
  
  

Inflammation of the Eyes

• Inflammation of the lining in and around the eyes and nose are the main symptoms that a cat experiences during a cat flu if it was caused by FHV-1, also known as rhinotracheitis. When the lining of the cat's eyes are inflamed, you will notice redness and swelling of the eyes and the presence of a discharge which eventually thickens and becomes filled with pus, according to Cats of Australia's website, an online resource about cats. Corneal ulcers may also develop in some cats.
  
  

Inflammation of the Nose

• When the lining of the nose becomes inflamed, you will observe excessive sneezing in the cat; in fact, "severe sneezing" is a significant and distinctive initial symptom of cat flu caused by the herpes virus, writes Wilma Lagerwerf, a registered veterinary and laboratory animal technician, in a Winn Feline Foundation article about upper respiratory viruses in cats. Sneezing is accompanied by a discharge that can change from clear to thick, green fluid if the cat is left untreated. Some felines may experience a decrease in their ability to smell due to the inflammation.
  
  Cats that have the flu as a result of getting FCV generally have nasal discharge but not to the same extent or severity as with FHV-1-affected cats, according to the Feline Advisory Bureau (FAB), another organization concerned about cat health and welfare.
  
  

Oral Ulcers

• Ulcers that develop in the mouth, tongue and nose are defining features of FCV-infected felines, according to Pawprints and Purrs. The presence of the ulcers causes a significant decrease in appetite and severe cases may lead to drooling, according to Cats of Australia. Some cats with oral ulcers may also have gum inflammation (gingivitis).
  
  

Other Signs

• Cats suffering from flu symptoms (caused by both FCV and FHV-1) may get a fever, refuse to eat or drink (which results in dehydration) and appear to be depressed.
  
  Since there are many viral strains of FCV, actual symptoms and the severity of them range widely depending on which strain is affecting the cat. For example, there are some FCV strains that cause limping, joint pain, pneumonia and breathing problems, explains Lagerwerf in another article about respiratory viruses published by the Winn Feline Foundation. Other FCV strains have been known to cause skin ulcers and even jaundice of the skin and gums, as stated by the Feline Advisory Bureau.