This fact sheet was taken from a fact sheet by Dr. Cynda Crawford, Clinical Assistant Professor University of Florida College of Veterinary Medicine.

1. What is canine influenza?
Canine influenza is a highly contagious respiratory infection of dogs caused by a novel influenza A subtype H3N8 virus that was first discovered in 2004.
2. Where does canine influenza occur?
Canine influenza has been documented in 30 states and the District of Columbia. At this time, the canine influenza virus (CIV) is very prevalent in many communities in Colorado, Florida, New York, Connecticut and Pennsylvania. We have seen at least one severe outbreak here in Fairfield County.
3. What type of infection does CIV cause?
Similar to influenza viruses that infect other mammals, canine influenza virus causes an acute respiratory infection in dogs. Unlike human influenza, canine influenza is not a “seasonal” infection; infections can occur any time of year.
4. What are the clinical signs of canine influenza?
Like influenza viruses for other species, CIV causes flu-like illness consisting of cough, sneezing, and nasal discharge. 100% of exposed dogs become infected; about 80% develop flu-like illness, while another 20% do not become ill. In past outbreaks between 1 and 8% of infected dogs have died. Fortunately, most   dogs recover within 2-4 weeks without any further health complications; however, some dogs progress to pneumonia, which is usually due to secondary bacterial infections. While the overall mortality rate for canine influenza is low, the secondary pneumonia can be life-threatening. There is no evidence for age or breed susceptibility for developing pneumonia during canine influenza.
5. Who is susceptible to canine influenza?
Because canine influenza is due to a virus that is novel to the canine population, all dogs lack preexisting immunity to the virus. Dogs of any breed, age or health status are therefore susceptible to infection. Canine influenza is most likely to spread in places where dogs congregate. Potentially, dogs in shelters, boarding and dog training facilities, doggie day care, dog shows, veterinary hospitals, pet stores, groomers and the dog park are at higher risk for exposure to CIV. Dogs that mostly stay at home and walk around the neighborhood are at low risk. CIV does not infect people, and there is no evidence that cats have become infected by exposure to dogs with canine influenza.
6. How is canine influenza transmitted?
As with other respiratory infections, the most efficient transmission occurs by direct contact with infected dogs and by aerosols generated by coughing and sneezing. The virus can also contaminate kennel surfaces, food and water bowls, collars and leashes, and the hands and clothing of people who handle infected dogs. Fortunately, the virus is easily inactivated by washing hands, clothes and other items with soap and water.
7. How is canine influenza diagnosed?
Canine influenza cannot be diagnosed by clinical signs because all of the other respiratory pathogens cause similar signs of coughing, sneezing, and nasal discharge. For dogs that have been ill for less than 4 days, veterinarians can collect swabs from the nose or throat and submit them to a diagnostic laboratory that offers a validated PCR test for canine influenza virus. The most accurate test recommended for confirmation of infection requires the collection of a small blood sample from the dog during the first week of illness, followed by collection of another sample 10 to 14 days later. The paired serum samples are submitted to a diagnostic laboratory for measurement of antibodies to CIV that were formed in response to infection.
8. How is canine influenza treated?
Since canine influenza is a viral infection, treatment consists mainly of supportive care while the virus runs its course, much like for human influenza. You should call us for an appointment if you suspect that your dog might have canine influenza. We can verify the diagnosis and determine what type of supportive care is needed, including whether antibiotics should be given for secondary bacterial infections. Dogs with pneumonia generally require hospitalization under the supervision of a veterinarian.
9. How contagious is canine influenza?
Like influenza infections in other species, canine influenza is highly contagious. 100% of exposed dogs will become infected. Infected dogs shed virus in their respiratory secretions for 7 to 10 days, during which time the dog is contagious to other dogs. Infected dogs that do not show symptoms are also contagious and dogs can start infecting other dogs several days before their symptoms start. Your dog can become infected without you even being aware they have been exposed. This also allows the virus to spread very quickly through a kennel or even an entire community. Once the virus has run its course, the dog is no longer contagious. Therefore, it is recommended that dogs with canine influenza be isolated from other dogs for two weeks to err on the conservative side. CIV does not cause a permanent infection.
10. Is there a vaccine for canine influenza?
In May 2009, the USDA approved the licensure of the first influenza vaccine for dogs developed by Intervet/Schering Plough Animal Health Corporation. The canine influenza vaccine contains inactivated whole virus, so there is no chance that the vaccine itself can cause respiratory infections. During tests to evaluate vaccine performance, there were no side effects or safety issues in a field trial including more than 700 dogs ranging in age from six weeks to 10 years and representing 30 breeds. The vaccine is intended as an aid in the control of disease associated with
CIV infection. Although the vaccine may not prevent infection, efficacy trials have shown that vaccination significantly reduces the severity and duration of clinical illness, the incidence and severity of damage to the lungs and the incidence of fatal and severe infections. In addition, the vaccine reduces the amount of virus shed and shortens the shedding interval. This means that vaccinated dogs that become infected have less illness and are not as contagious to other dogs. These benefits are similar to those provided by influenza vaccines used in other species, including humans.
 
We recommend the canine influenza vaccine for dogs at risk for exposure to CIV, including dogs that are boarding, attending doggie day care, the groomer, dog parks, dog training, and dog competitions. We recommend the canine influenza vaccine in dogs that are already receiving the kennel cough vaccine for Bordetella because the risk groups are the same. The initial vaccinations are a series of 2 given 2-3 weeks apart followed by annual boosters and can be given to dogs as young as 6 weeks of age. Please call us to discuss whether your dog is at risk for exposure to CIV, and would benefit from the canine influenza vaccine.