Canine Influenza Fact Sheet

According to the American Veterinary Medical Association (AVMA), “Canine influenza is a highly contagious respiratory infection of dogs that is caused by an influenza virus”.


More on this disease below.


Two Strains


There are two strains of the canine influenza virus.  The first, labeled H3N8, was reported in 2004 and is thought to have mutated from an equine strain of Type A flu virus.  The second, labeled H3N2, was first identified during a 2015 Chicago outbreak of the disease.  According to the AVMA, “The strain causing the 2015 outbreak was almost genetically identical to an H3N2 strain previously reported only in Korea, China and Thailand. In [these countries], this H3N2 strain is believed to have resulted from the direct transfer of an avian influenza virus to dogs. Since March 2015, thousands of dogs have been confirmed positive for H3N2 canine influenza across the U.S.”


Why is it called an ‘A’ virus?


There are three kinds of flu virus.


Type A:  Thought of as the most infectious and virulent, Type A flu can infect humans and other animals like horses, birds, pigs, and dogs.  It is typically associated with wide outbreaks of disease and in humans, has caused the most death.


Type B:  The Type B virus typically only infects humans. It is less likely to mutate and incidences of widespread sickness associated with this virus are less frequent than outbreaks caused by Type A.


Type C:  This type is the mildest of the three types.  Infected patients show no symptoms or mild symptoms of sickness.


H3N2: What Do The H and the N Stand For?


The H and the N are the first initials of two proteins located on the surface of the virus that are critical to infection. The first one, called hemagglutinin, unlocks the cells inside your dog’s respiratory tract and allows the flu entry into the cell where it replicates.  The second, Neuraminidase, is used to reopen the cell wall from the inside allowing the newly created viruses to escape into your pet’s body where they go on to reinfect other cells and repeat the process anew.


If Only It Were That Simple


To complicate things a bit, there are 11 identified versions of the H protein and 9 different identified versions of the N protein.  The numbers following the letter in the strain’s name indicate which of the H and N proteins are present on the surface of the virus.  The variations in these proteins are important because they are how your dog’s body recognizes and ultimately fights the virus. They also characterize the virus’s virulence; the host it infects; it’s communicability, and so forth.


How Bad Is Canine Flu?


The American Veterinary Medical Association has identified two clinical syndromes with respect to canine flu:  a mild form and a severe form.


Mild Form:  Symptoms can include coughing, lethargy, fever, reduced appetite, and watery discharge from the eyes.  It is not uncommon for dogs to have a thicker discharge from the nose often associated with a secondary infection. Coughing in dogs can persist for 3 weeks or longer after infection.  The symptoms are in many ways identical to those of more familiar dog illness, Kennel Cough.


Severe Form:  The severe form is associated with the above-mentioned symptoms along with a very high fever (104-107 degrees …a dog’s ‘normal temperature is 101-103 degrees) and pneumonia-like symptoms. The severe form can be deadly.

Our very own Dr. Freda discusses the flu with the Fox 5 team

How Is Canine Flu Treated?


Patients are first examined and diagnosed by one of our East Side veterinarians after which a treatment plan is built based on the patient’s breed, size, age and symptoms.  The treatment plan may include supportive therapy and antibiotics to guard against secondary infection.  Patients that suffer from the severe syndrome of canine flu may require hospitalized in isolation due to the disease’s highly infectious nature.


Is There A Vaccine For Canine Influenza?


Yes, a vaccine against the H3N8 strain was developed in 2009.  In 2015, two more vaccines were released; these for protection against H3N2 which is the strain that’s currently infecting city dogs.  The vaccine is initially given in two doses spaced two weeks apart, but immunity is not acquired by the dog for an additional two weeks after the last dose.  In other words, it will be 24 days after the dog’s first dose before he or she is fully protected.


How Do Dogs Acquire Canine Flu?


Canine flu is highly contagious.  It can be transmitted by direct contact with an infected animal or by objects that have been contacted by an infected animal.  To date, no people have been known to contract canine influenza and according to the Shelter Medicine School of Veterinary Medicine in Madison, Wisconsin, only 8 cats have contracted H3N2.  In the cat cases, symptoms were mild and all cats recovered.  According to the school, they are hopeful that ‘feline infections continue to be very rare’.


How Do I Keep My Dog Safe During An Outbreak?


In a crammed city like New York, trying to steer your dog clear of possible sources of infection are difficult if not impossible.  More than 90% of patients infected with influenza recover, but there are enough patients that become very ill or even die that a reasonable amount of concern on behalf of all pet parents is warranted.  Certainly if your dog has not been vaccinated, he or she should be.  The vaccine is effective and safe.  If your dog begins to cough or experiences other cold-like symptoms, you should call us, alert us of your concerns, and make an appointment for an examination.  If your dog has symptoms of or is diagnosed with influenza, you should not allow your dog to interact with others.



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