5 Things to Know About Dog Flu

Canine influenza virus (CIV) is thought to have mutated from a virus originally causing respiratory illness in horses.

Dog flu is extremely contagious from dog to dog. By: DEWEGGIS

There’s a dog flu epidemic in Chicago, and the numbers are climbing. Symptoms of the canine flu started appearing in January, and it has been spreading quickly ever since. According to the Cook County Department of Animal and Rabies Control, 5 dogs have died and more than 1,000 have been diagnosed with the disease.

As a result of the dog flu outbreak, which hasn’t happened in the city since 2008, boarding kennels are closing, dog parks have warning signs posted, and outdoor events involving dogs have been canceled.

It can be difficult to determine your dog’s risk of contracting the flu or what steps you should take, so in this article we’ll cover what you need to know.

Canine influenza (dog flu) was first noted in 2004 in a kennel of racing Greyhounds, which makes it a relatively “young” disease.

This particular flu virus is thought to have mutated from a virus causing respiratory illness in horses. Although it may make your pet feel sick, the H3N8 virus has never been found to cause infection in people.

In much the same way that flu hits some people harder than others, canine influenza is an unpleasant illness from which most dogs recover, but a small percentage of patients develop secondary problems such as pneumonia. In an elderly or weak dog, these complications could be potentially life-threatening.

1. Symptoms

The signs of dog flu are those of a severe cold:

  • Coughing
  • Sneezing
  • Runny nose
  • Appetite loss
  • Fever

These symptoms are quite general, but the severity of the illness sets it apart from other infections. Even strong dogs are likely to be under the weather for several days before eventually bouncing back.

Older dogs or those with another health issue (such as diabetes or Cushing’s disease) are at greater risk of developing complications because their immune system is already weakened, so they are less able to fight off chest infections. Signs of this include labored breathing and extreme lethargy, so severe that the dog doesn’t want to get out of bed. If your dog shows these signs, contact your veterinarian immediately.

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2. Causes

Canine influenza virus (CIV) is a mutation of a virus causing respiratory illness in horses.

Although the virus made the jump from one species to another (horses to dogs), to date there is no evidence that an infected dog poses a health risk to people.

3. Diagnosis

Because of the general nature of the signs (coughing, sneezing, fever and runny nose), it is not possible to reach a diagnosis of canine influenza based on symptoms alone.

Knowing the exact nature of the infection is not always required (it doesn’t change the treatment), but this can be ascertained by swabbing the mouth or throat and sending the swab away for special tests.

An alternative is to take 2 blood samples — one at the height of the symptoms and the other on recovery — and test for an immune response to CIV.

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4. Treatment

Because canine influenza is viral, there is no specific treatment that kills the virus.

Treatment is based around nursing care such as:

  • Keeping the eyes and nose clean
  • Encouraging the dog to eat
  • Keeping him comfortable

If the patient is doing especially poorly and not drinking, he may need intravenous fluids to support him during this difficult time. Likewise, controlling secondary chest infections with antibiotics is an important part of helping elderly dogs or those more vulnerable to complications.

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5. Prevention

A vaccine is available that reduces the severity of canine influenza should your dog be at risk of coming into contact with the virus.

This is not a core vaccination, however, which means it is not given routinely but rather on the basis of a risk assessment. If canine influenza is something that concerns you, speak with your vet about the suitability of your pet for vaccination.

The flu virus is highly infectious and can be picked up by indirect contact. The virus can survive in and on surfaces, where it poses a risk for dogs who come along and sniff or lick.

Good hygiene is essential — such as washing your hands after touching other dogs (to avoid the risk of transfer) and wiping down surfaces with disinfectant. If there is an outbreak of flu in the area, as there is in Chicago right now, it is sensible to limit your dog’s contact with other dogs.


  • “Influenza A virus (H3N8) in dogs with respiratory disease.” Florida. June 2008. Sunchai, Crawford, Kuou et al. Journal of Emerging Diseases, 14(6).


This pet health content was written by a veterinarian, Dr. Pippa Elliott, BVMS, MRCVS. It was last reviewed April 7, 2015.

Dr. Pippa Elliott, BVMS, MRCVS

View posts by Dr. Pippa Elliott, BVMS, MRCVS
Dr. Pippa Elliott, BVMS, MRCVS, is a veterinarian with nearly 30 years of experience in companion animal practice. Dr. Elliott earned her Bachelor of Veterinary Medicine and Surgery from the University of Glasgow. She was also designated a Member of the Royal College of Veterinary Surgeons. Married with 2 grown-up kids, Dr. Elliott has a naughty puggle called Poggle, 3 cats and a bearded dragon.

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