Feline Herpes Virus (Cat Flu)

At a glance

Feline herpesvirus and calicivirus are the two most common causes of upper respiratory infections in cats.

  • About: Feline herpes is a highly contagious upper respiratory infection caused by the feline herpesvirus (FHV-1). Kittens and senior cats are most at risk.
  • Symptoms: Nasal discharge, sneezing, fever, loss of appetite, drooling and corneal ulcers.
  • Diagnosis: Presenting symptoms and a nasal or eye swab sent for PCR testing.
  • Treatment: Nutritional and fluid support, remove discharges from the eyes and nose antiviral medications.

What is feline herpesvirus?

Also known as feline viral rhinotracheitis (FVR), feline herpes is a highly contagious upper respiratory disease of cats caused by feline herpesvirus type 1 (FHV-1). An upper respiratory disease refers to infections in the area of the eyes, nose, throat and sinus areas. It is similar to a cold/flu in humans.

Feline herpesvirus is the most common cause of upper respiratory disease in cats, kittens, cats in stressed/overcrowded environments such as animal shelters and multi-cat households are at increased risk. Once your cat becomes infected with the feline herpesvirus he will have it for life.

The first outbreak is usually the most severe. Once recovered, in the healthy cat the immune system usually manages to keep the virus in check, but there may be the occasional outbreak at times of stress (pregnancy, lactation, overcrowding, while boarding etc.) or sickness. Corticosteroid injections can also bring on an outbreak in the infected cat.

The distribution of feline herpesvirus is worldwide.

How does feline herpesvirus affect your cat?

The virus infects and grows in the nose, eyes, sinus, throat, mouth, and tonsils of a cat which causes inflammation and fever. Due to the nasal discharge, the cat’s sense of smell is severely diminished, causing his appetite to wane, while the loss of appetite is dangerous in all cats, it is especially so in kittens.

Due to the damage caused to tissues, a secondary bacterial infection can take hold.

If a pregnant cat catches herpes, it can lead to the abortion of the kittens.

How is feline herpesvirus transmitted?

Feline herpes can be spread by direct or indirect contact, the virus can survive for up to 18 hours in the environment.

  • Vertical: The feline mother can pass feline herpesvirus onto her unborn kittens.
  • Aerosol: Inhalation of sneeze droplets that contain the virus.
  • Direct contact: Saliva, eye and nasal secretions.
  • Fomites: Food bowls, caregiver clothing, litter trays, toys and bedding which have been in contact with an infected cat.

Asymptomatic/latent carriers may shed the virus, which means that while they are displaying no symptoms themselves, they are actively shedding the virus and other cats can become infected.

Clinical signs

The incubation period of feline herpes is between 2-5 days after exposure. Kittens, seniors and immuncompromised cats typically experience more severe symptoms than healthy adult cats.
feline herpes symptoms


A presumptive diagnosis of feline herpesvirus or calicivirus may be made based on clinical signs.  While both viruses cause upper respiratory infection, there are variations, for example, calicivirus typically causes ulcers in the mouth, whereas feline herpesvirus causes ulcers in the eye.

  • Polymerase chain reaction: A test to look for genetic material from the herpesvirus from an ocular or oral sample.
  • Baseline tests:  Biochemical profile, complete blood count, and urinalysis which cannot diagnose feline herpesvirus but can provide information on the overall health of the cat.


The goal of treatment is to give supportive care, manage symptoms and try to shorten the duration of the outbreak.

Systemic antiviral drugs:

  • Famciclovir is a medication that converts to penciclovir and then to penciclovir triphosphate. Penciclovir triphosphate inhibits DNA polymerase and selectively inhibits viral DNA replication.
  • Interferon is a naturally occurring protein made by cells of the immune system in response to certain viral infections. They do not kill the virus but bind to infected cells as well as neighbouring uninfected cells, which stimulate them to produce proteins that prevent the virus from replicating.

Antiviral eye ointments:

  • Trifluridine, cidofovir, idoxuridine and vidarabine eye drops or ointment for cats with corneal ulcers and conjunctivitis.

Broad-spectrum antibiotics:

  • Antibiotics are ineffective against the herpes virus but can prevent or treat secondary infections that may occur.


  • An essential amino acid that can suppress viral replication as well as inhibit cytopathogenicity. It is available in a palatable paste form from most pet stores and veterinarians. The typical dose of L-Lysine is 400-500 mg per day. Always speak to your veterinarian before administering supplements.

Supportive care:

In addition to medical therapy, supportive care is critical for cats with herpes. Loss of appetite (anorexia) and dehydration are common and impact the cat’s ability to fight the virus.

  • Fluid therapy: Subcutaneous or intravenous fluids that can prevent or treat dehydration.
  • Nutritional support: This can include offering a highly palatable diet or paste or a feeding tube for cats who refuse to eat.

Uncomplicated feline herpes usually resolves within 7-10 days.

Home care

  • Administer all medications as directed by your veterinarian.
  • If you have other cats in the household, quarantine the infected cat until it has recovered.
  • Ensure the cat receives adequate food and liquid intake. Nutritional support can include offering highly palatable foods (warmed, if necessary), appetite stimulants or if the cat refuses to eat, a feeding tube will be necessary.
  • Subcutaneous fluids to treat and prevent dehydration. The veterinarian can show you how to administer sub-q fluids.
  • Ease breathing and discharge with vaporizers, if you don’t have a vaporizer, run a hot shower until the room is steamy and leave your cat in the bathroom for 10-15 minutes.
  • Remove eye discharge and crusting with gauze and a warm saline solution.
  • Keep the nostrils and eyes clear of discharges. Use cotton balls dipped in warm water to wipe away any discharge.
  • Apply Vaseline to the nose.


Feline herpesvirus is fragile and can only live for 18 hours on surfaces. The following disinfectants are effective against FHV-1.

  • Bleach (sodium hypochlorite, calcium hypochlorite or sodium dichloroisocyanurate)
  • Benzalkonium chloride and polyhexanide
  • Virox, Accel – Accelerated hydrogen peroxide
  • Trifectant or Virkon-potassium peroxymonosulfate
  • Ethanol 75%


The best way to prevent feline herpes is to have your cat vaccinated. Kittens should receive their F3 vaccination at 8, 12 and 16 weeks of age, then receive a booster at 12 months followed by tri-annually after that or as your veterinarian recommends.

Quarantine new cats for 7-10 days before introducing them to resident cats.

Frequently asked questions

My vaccinated cat caught cat flu:

If a cat contracts herpes before receiving a vaccination, the virus will remain with your cat for life. Most of the time it is dormant (latent stage), but at times of stress or sickness, the virus can reactivate, causing symptoms.

Is feline herpes contagious to humans?

No, you can not catch feline herpes from your cat, only domesticated cats, and close relatives can catch feline herpesvirus. There are several types of herpes virus to infect humans but they are not the same as feline herpes.

Is feline herpes contagious to other cats?

Yes, feline herpes is extremely contagious and carers must isolate cats with herpes to prevent transmission.

Can cats catch cold sores from humans?

Just as humans can’t catch feline herpes, cats can’t catch cold sores (which are caused by a herpes virus) from humans. All herpes viruses are host specific and do not cause infection in other species.

Is feline herpes fatal?

It can be, particularly in young kittens. Infected cats must receive supportive care while their own body fights the virus.

Is there a cure for feline herpes?

Once a cat is infected with the herpes virus, it has it for life. After the initial infection, the virus lays dormant, primarily in the trigeminal ganglion and to lesser degrees in the cornea and nasal cavity. Flare-ups can occur during times of stress, such as a trip to the veterinarian or a stay at a boarding facility.


  • Julia Wilson, 'Cat World' Founder

    Julia Wilson is the founder of Cat-World, and has researched and written over 1,000 articles about cats. She is a cat expert with over 20 years of experience writing about a wide range of cat topics, with a special interest in cat health, welfare and preventative care. Julia lives in Sydney with her family, four cats and two dogs. Full author bio

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