Update on Canine Influenza Virus


In March 2015 Chicago was making national news due to large numbers of dogs becoming sick with a respiratory illness. In the beginning of this outbreak, the dogs who were becoming ill were active and social family members, not shelter dogs. These dogs felt quite ill and were very lethargic, did not want to eat and had a terrible cough along with nasal discharge. Some of these dogs were developing pneumonia. Hundreds of dogs fell ill in a short period of time and soon shelters were also severely affected. Laboratory testing done at Cornell University discovered that the reason why so many dogs were getting ill was due to a new strain of canine influenza virus, also called the “flu.” Because this was a new virus, none of our dogs had any immunity to it. Additionally we learned that dogs are contagious before they show any signs of illness. For these reasons the virus was spreading in epidemic proportions. Today this new flu virus remains active in our Chicagoland area with periodic reports of dogs falling ill to canine influenza.

Is there a canine influenza vaccine?

Yes there is a vaccine, but during the flu outbreak in spring 2015 the only canine influenza vaccine that was available was developed for a different strain of influenza. Scientist classify influenza viruses by certain proteins on the viruses’ surface. This new virus is classified as H3N2 but the only vaccine available in the spring was to protect against the H3N8 strain. We now know that there is no cross-reactivity of immunity between these two strains. This means that if your dog is vaccinated for one strain they will not develop an immunity for the other strain. Luckily in November 2015 a new vaccine was released to protect our dogs from the new H3N2 strain.

New vaccine available – should I get my dog vaccinated?

In preliminary studies this vaccine is proving to be safe and effective in minimizing the illness. Similarly the previous influenza vaccine has been safe and effective during its use for almost 10 years. It is recommended that any dog that is social or has a housemate that is social should get vaccinated. A social dog is one that goes anywhere other dogs are or have been. Essentially this includes most of our canine friends but dogs especially at risk are ones that go to dog parks, boarding facilities, day care, grooming, obedience training, agility training, dog shows or visit the pet store or veterinary hospital. The influenza virus can live in the environment for 2 days and can stay on a person’s clothing or shoes for 12 to 24 hours. This means dogs can become infected even if there is no direct contact with another dog.

Current Vaccine Recommendations for Social Dogs

Canine Influenza Vaccine Information - Loyal-Companions.com

The virus is also easily transmitted by a cough or sneeze. With normal cleaning and disinfecting the influenza virus is easily killed. There continues to be reports of dogs contracting the new H3N2 strain of influenza in the Chicagoland area. Dogs that become ill with the new strain are generally much sicker than what had been observed previously with canine influenza. Dogs run higher fevers and have more severe coughs and nasal discharge. Also the dogs develop pneumonia more frequently. There have been deaths reported with the new H3N2 strain but fortunately most dogs recover. The recovered dogs have been shown to be contagious for 3 weeks which is much longer than the 7 – 10 day contagious period associated with the older H3N8 strain. Because dogs become much sicker, are contagious longer and there are continued reports of the H3N2 causing illness in the Chicagoland area it is advisable to vaccinate your social dog.

Should you vaccinate your dog against the flu? What you need to know.

Should my dog be vaccinated for both strains of influenza?

Some veterinarians are recommending vaccinating for both strains which would provide the best assurance for your dog to not become ill from influenza. Other veterinarians do not recommend any influenza vaccines because in their area of the country there have not been any influenza outbreaks. After dogs receive their first influenza vaccine they will need a booster shot in 3 weeks and then an annual vaccine thereafter. Currently there is not a vaccine that combines both strains of influenza so dogs will need to receive individual shots for each strain. Currently in the Chicagoland area the new H3N2 strain is still being diagnosed with some frequency and the older H3N8 strain is diagnosed more rarely. Evaluating your dog’s lifestyle and the frequency of their social interactions should help guide your decision on if your dog should receive both influenza vaccines.

What other respiratory illnesses can my social dog contract?

There are many respiratory illnesses that social dogs can be exposed to – very similar to school age children. In fact there are 10 viruses and bacteria that are known to cause respiratory illness in dogs. Often these illnesses are collectively called “kennel cough.” The more accurate terminology is “Canine Infectious Respiratory Disease” or CIRD. The CIRD complex includes both influenza strains as well as viruses such as distemper, adenovirus, parainfluenza and the bacteria Bordetella. When a social dog develops a cough with a nasal discharge veterinarians cannot distinguish which of the 10 viruses and bacteria may be the culprit unless they send tests to a diagnostic lab to determine the causative organism. Prior to the influenza outbreak, the virus called parainfluenza was causing most of the respiratory illness in the dogs that had samples sent to CornellUniversity. During the influenza outbreaks in Chicago, Atlanta and North Carolina there was a huge surge of samples from sick dogs being sent to Cornell University. This allowed for the detection of the new strain of influenza but it was also determined that parainfluenza continues to be the culprit in many of the respiratory illness cases. Interestingly dogs receiving the injectable form of the parainfluenza vaccine were still getting sick from the virus. Dogs that receive the intranasal form of the parainfluenza vaccine seem to have better protection. Parainfluenza is a component of the intranasal “kennel cough” vaccine that is also called the Bordetella vaccine.

How can I protect my dog from respiratory illnesses?

The best way to protect your dog from respiratory illnesses is to vaccinate. The distemper vaccine is important in protecting dogs from the very severe respiratory illness of distemper. Bordetella is a bacteria that can cause signs on its own or while there is other viral infection. The Bordetella vaccine provides dogs with reliable protection and it is thought that the intranasal form provides the best immunity. Parainfluenza has been shown to be an important player in respiratory illness and dogs develop the best immunity from the intranasal form of this vaccine. Parainfluenza is combined with Bordetella in the intranasal vaccine. Canine influenza vaccines are available for both strains, with the new H3N2 being the more severe illness and currently the most prevalent in the Chicagoland area.


A new strain of canine influenza virus referred to the H3N2 strain caused hundreds of dogs to become very ill in the Chicagoland area in the spring of 2015. In November 2015 a new vaccine was made available to help protect our social canine friends from the new H3N2 strain. Many of our dogs are social animals having interactions with other dogs or visiting places where other dogs have been. This puts our dogs at risk for contracting respiratory illness, coughing and nasal discharge, that are part of the Canine Infectious Respiratory Disease complex or CIRD. In the past this had been generally referred to “kennel cough.” The dogs that are most at risk are ones that go to dog parks, boarding facilities, day care, grooming, dog shows, obedience or agility training, play dates with friend’s or neighbor’s dogs or a simple visit to the pet store or veterinary hospital. Vaccination is the best way to protect dogs from respiratory illness. Canine influenza and the other viruses and bacteria of the CIRD complex continue to play an important role in causing coughing and nasal discharge in our dogs. In the past, the virus called parainfluenza has been a common culprit and it appears that dogs gain the best protection when receiving an intranasal form of this vaccine. Discuss with your veterinarian your dog’s social lifestyle and the best way to protect your dog from respiratory illness.


Richardson JA, Glaser A, Reine-Salz N, Dubovi EJ. Prevalence of canine infectious respiratory disease in dogs in Chicago outbreak (March-April 2015) ACVIM Forum Proceedings, June 2015.

VETgirl Webinar, “Canine Influenza Virus and Vaccine Update.” December 7, 2015.

Jane E. Sykes, BVSc, PhD, DACVIM. “Infectious Diseases” CVMA lecture. December 9, 2015.