Understanding Cat Flu

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Last updated 8/2/2025

cat flu
feline herpes virus
feline calicivirus
cat symptoms
cat health

What is Cat Flu?

Cat flu is a common illness in cats, affecting their upper respiratory system. It's usually not deadly for healthy adult cats, but it can be serious for kittens and older cats with weaker immune systems.

The two main viruses causing cat flu are:

  • Feline Herpes Virus-1 (FHV-1)
  • Feline Calicivirus (FCV)

Feline Herpes Virus is more severe and known for infecting the eyes and respiratory tract. Cat flu spreads quickly from one cat to another.

Symptoms of Feline Herpes Virus

The Eyes

This virus can cause conjunctivitis, where the eyes swell and turn red. Discharge, sometimes pus-filled, may occur, and corneal ulcers can develop.

The Nose

Cats might sneeze frequently. Nasal linings can become inflamed, resulting in runny noses that turn thick and green. Cats might lose their sense of smell.

Fever and Loss of Appetite

Infected cats often have a fever and feel unwell, losing their appetite and sometimes becoming dehydrated. They might refuse to drink.

Pregnancy

A pregnant cat infected with this virus might abort her kittens. If born, the kittens can catch the virus from their mother.

Symptoms of Feline Calicivirus

The Mouth and Tongue

This virus causes ulcers on the mouth, tongue, palate, gums, and sometimes the nose. Cats might drool due to painful ulcers.

The Nose and Eyes

Symptoms resemble a cold with a runny nose and eyes but without eye ulcers.

Fever and Depression

The cat might or might not have a fever. Painful ulcers can lead to a loss of appetite, and pneumonia may occur from secondary infections.

The Joints

Joint pain may cause limping, a syndrome reported with this virus. Limping can switch from one leg to another.

The Paws

Some FCV strains cause ulcers in the paws.

Diagnosis and Treatment of Cat Flu

Your vet can diagnose cat flu based on symptoms and confirm it with lab tests. Treatment focuses on comfort and managing symptoms:

  • Eye drops and ointments for eye issues
  • Warm saline for cleaning eyes and nose
  • Antibiotics for bacterial infections
  • Pain management for mouth ulcers
  • Hydration support, possibly with intravenous fluids

Encourage eating with strong-smelling foods if the cat loses its sense of smell.

How Cat Flu Spreads

Infected cats should stay isolated as the virus spreads through cat-to-cat contact, nasal and eye discharge, and sneezing. It can also spread via contaminated items or even humans who have been in contact with an infected cat. The virus can live on surfaces or objects for several days.

Duration and Carrier State

Cat flu symptoms usually last 7-14 days, but cats might still carry the virus. Cats with FHV might carry it for life, while FCV carriers usually clear the virus within months, though some may take up to 18 months.

Preventing Cat Flu

Vaccinations for FHV-1 and FCV are available. Discuss vaccination plans with your vet to protect your cat from cat flu.