Canine Influenza

Do you mean that my dog can get the flu?

Well, not “the” flu that people get, but he can become infected with Canine Influenza.

H3N8 is the standard nomenclature for the virus that causes influenza in dogs. To help you relate, think of swine flu as H1N1. Or bird flu as H7N9 or H7N2.  They are all “Influenza A” viruses. Influenza viruses in that group also cause symptoms in birds, horses, pigs and people.
(Click here to read another post about Canine Influenza that focuses on vaccination/prevention.)
(Click here to read an update posted June 12, 2015, including information about the 2015 Chicago Canine Influenza epidemic.)


The disease was first reported in March, 2004. Early cases mostly affected racing greyhounds and dogs in humane shelters. Clearly, these are both groups that are housed in large numbers close together. Under such conditions contagious diseases are transmitted easily and rapidly.

Canine Influenza, or CI, is dangerous to dogs because, as in people, some cases will result in fatalities.  About 8% of dogs who contract Canine Influenza will die.


Thirty-eight states have reported cases of CI. Even so, most dogs nationwide have immune systems “naive” to this disease. In other words, dogs who have never been exposed to the disease have no way for the immune system to be ready in advance to respond to the illness.


Signs of CI mimic those of other respiratory tract diseases such as Infectious Canine Tracheobronchitis. Your dog may have a soft, moist cough that is productive, or a harsh, hacking, dry cough. Most dogs have a low-grade fever, nasal discharge, lethargy and inappetence. Some dogs, however, about 20%, will suffer more severe signs including a high fever and pneumonia. Complications can lead to fatalities.

Definitive diagnosis is complex. Within a week of clinical signs a test called PCR (polymerase chain reaction) can be performed to look for evidence of the virus itself. After seven days a different test must be used, one that looks for the immune system’s response to the infection. That test must be paired, taking two samples two weeks apart and evaluating for a rising level of response (titer). A combination of physical examination, screening laboratory tests (use H-F-O-R-M-L [no dashes] as a search term in the upper right hand corner of this page) and chest X-ray may also lead your pet’s doctor to suspect Canine Influenza.


All dogs are at risk, regardless of breed or age except those who have been infected and survived and those who have been vaccinated against CI. (Always remember that no vaccine is perfect, and even some properly-vaccinated dogs may not produce protection from the vaccine.) Some factors increase an individual’s risk, however:

  • racing greyhounds adopted from or previously raced in Florida
  • shelter dogs, especially those adopted from Florida
  • dogs who attend boarding kennels and/or doggy day care
  • dogs in competitions, such as agility and field trials


Like the flu humans get, Canine Influenza is passed by direct contact, such as dogs “checking out” each other. It can also be airborne, so even dogs kenneled together in a room but never having physical contact can infect each other. The virus is spread in large quantities by coughs and sneezes. Fomites can be factored in as well, such as  sharing food and water bowls and bathroom sites. A pet owner with an infected dog may carry the germ on his hands, clothing and other inanimate fixtures around the home.  The virus survives on clothing and other soft, porous fomites for up to 24 hours, hard surfaces up to 48 hours.

20% of dogs exposed to canine influenza can become silent carriers of the virus and transmit it to other dogs.


As with other viral respiratory tract infections in dogs, cats and humans, there is no specific treatment for the virus, but supportive treatment can help fight secondary bacterial invaders, dehydration and cough. Most dogs live through the infection with proper symptomatic treatment.


As with any disease, good overall health, frequent exercise, regular doctor visits, a temperature-controlled housing environment free from drafts and top quality food are first-line steps to a healthy pet.

A vaccine is available.  If your veterinarian feels your dog is at risk he can administer the vaccination for your pet.


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