Reviewed by Dr. Fiona Lee
Flu season is coming, and that means getting flu shots for the whole family – including your four-legged family members. Dogs can get the flu too, it's just a different influenza virus than the flu you can catch. In fact, your veterinarian may even recommend that your pup gets her own flu vaccine!
But just how serious is canine influenza? Is it contagious? What are the symptoms? This guide will answer all your questions about dog flu, helping you and your furry family be prepared.
What is canine influenza (dog flu)?
Influenza viruses are rthomyxoviruses that are host-specific, meaning each particular strain likes to infect one type of animal (or human!). They are prone to mutating, or changing, to adapt to a new host species however. Influenza viruses circulate worldwide.1
Canine influenza—or “dog flu"—is a highly contagious respiratory virus known as Type A influenza.2 It spreads among dogs, but can also affect cats.1 It was discovered in 2004 and has two strains identified in the U.S.: H3N8 and H3N2. Scientists believe both strains originated from viruses infecting other species and mutated to be able to spread among dogs.2
The strain H3N8 was first found in racing greyhounds and is believed to have jumped from horses to dogs. It was known to infect horses for 40 years prior mutating to a strain capable of causing illness in dogs.3 Alternately, the H3N2 strain was found in the U.S. in Chicago in 2015, but it was first identified in dogs from Asia in 2006.2 The strain is believed to have mutated from primarily infecting birds, to being capable of infecting dogs as well.
Is dog flu similar to human flu?
Canine influenza is similar to the human flu in many ways, including symptoms and method of transmission.2 One significant difference between dog flu and human flu is that technically there is no “flu season" for canines since infections occur year-round. In some ways, dog flu is similar to “kennel cough" which is caused by either a bacterial or viral infection and may infect dogs any time of year.2
Another important difference between the human flu and canine flu is that our collective human population has many antibodies. We are often exposed to the flu each season and many of us are vaccinated each year. In dogs, this virus is still pretty novel, or new. This means there is minimal 'herd immunity'. If this virus gets into a naïve population of dogs, the chances of causing illness are very high.
Average Bordetella & Canine Influenza Treatment Costs*
| Condition | Dog | Cat |
| Bordetella (Kennel Cough) | $418 | $596 |
| Canine Influenza | $271 | - |
*Pets Best 2021 claim data
What are the symptoms of canine influenza?
For the most part, dog flu symptoms are similar to human flu symptoms:
- Coughing
- Sneezing
- Runny nose
- Fever
- Loss of appetite
- Lethargy
Fortunately, many dogs will be asymptomatic and show no canine influenza symptoms at all. These dogs, however, are contagious and can spread the canine flu to other dogs. In serious cases, according to the Centers for Disease Control (CDC), dog flu can result in pneumonia, and in rare cases, death.4 If a dog is developing a severe case of pneumonia, he may have a higher fever from 104°F to 106°F or show more labored breathing.2
Diagnosing dog flu
If you think your dog has canine flu, or has a known exposure to the flu, you should seek medical attention immediately. Because flu symptoms in dogs are similar to the common cold or other respiratory illnesses, your veterinarian will need to administer a test to properly diagnose canine flu.
A PCR test can identify which strain is infecting your dog, which can be helpful since some evidence suggests that the H3N2 subtype is more virulent, causing more morbidity and mortality than H3N8.1 Clinical signs may also become more severe earlier with H3N2 compared to H3N8, and clinical signs may last for a longer duration.1
While you are waiting for test results, you should isolate your dog from other dogs and cats just to be safe.
How is canine influenza spread? How contagious is dog flu?
So, how can your dog catch dog flu? Much the same way people catch the flu.
Droplets
Canine influenza is transmitted by droplets or aerosols in the air. This means the flu can be spread through coughing, sneezing and barking. Dogs are at risk if they come in close contact with infected dogs, particularly in kennels, doggy daycare, shelters or groomers.
Objects
In addition, dog flu can be spread through objects such as food and water bowls, collars, leashes, toys and even indirectly through people who have come in contact with a contagious dog.
Surfaces
The virus can stay alive on surfaces for up to 48 hours, and on hands for 12 hours, so it is important to wash your hands and any objects that may have come in contact with your infected dog.2
Contact
The virus is very contagious, so if another dog has the flu, chances are likely that dogs around him will catch it too.2 Cats can even catch the virus too, although they are not thought to have prolonged shedding time and rarely get as sick as their canine counterparts.5
Canine influenza isn't currently widespread, so most dogs won't ever be exposed to canine influenza. This might change in the future since cases have been increasing in the U.S. Currently outbreaks are mostly confined to shelters, but this may change over time.6
Can people catch canine influenza?
Canine flu poses no risk to humans.2 The CDC reports that there hasn't been a single case of a human catching canine influenza anywhere in the world, including the U.S.4
The CDC does caution, however, that because influenza mutates rapidly, there's always a chance this could change. But there's no reason to be concerned about catching dog flu if your pup has it.
What about the reverse? Can dogs get the flu from humans? Some studies have shown that on rare occasions this may happen, such as with H1N1 in 2009.7 But it's not common.
How is canine influenza treated? Can it go away on its own?
If your dog is diagnosed with canine flu by a veterinarian, the treatment options will vary depending on factors including severity of symptoms, your dog's overall health, age and any pre-existing risk of respiratory illness.
Treating symptoms
For the most part, treatment is aimed at alleviating symptoms—just like when you have the human flu. Most dogs will recover within two to three weeks, but there is always the risk of secondary infections which may require additional diagnoses and treatment.
Medication and fluids
Depending on the severity of your dog's symptoms, your veterinarian may prescribe medication or administer fluids to prevent dehydration. For mild cases, the illness may just go away on its own and you'll just want to make sure your dog has plenty to drink and is given time to rest and stay comfortable.2
Treating secondary infections
If a secondary infection is suspected or your dog is at higher risk of serious illness due to comorbidities, he might be given antibiotics, NSAIDs to reduce inflammation or additional fluids.2 Although antivirals are available for the human flu, there are no antivirals for canine flu.2
If you suspect canine flu, bring your dog to the veterinarian as soon as possible, and don't forget to tell them you suspect canine flu so they can take proper precautions to avoid infecting other patients. Even though the case may be mild, you'll want to consult a veterinarian so you can make sure your dog is getting the right treatment and care.
How can I prevent canine influenza?
The best prevention is a combination of avoiding highly dog trafficked areas such as grooming, boarding, and training facilities, and animal shelters and to consider vaccination.
Dog Flu Vaccine
The canine influenza vaccine has proven to be effective at significantly decreasing the severity and degree of illness and viral shedding.6
Isolation
Preventing spread can be achieved with isolation. Since the canine flu is so contagious, infected dogs should be isolated from other dogs and cats for at least four weeks.3 You'll want to isolate other dogs in your household too.
If your dog is frequently around other dogs, then she's likely at higher risk of exposure. In those situations, considering vaccination makes sense, discussing the pros and cons with your veterinarian is a good idea.
What's the mortality rate for canine influenza?
The good news is that the vast majority of canine influenza cases are mild. In fact, the mortality rate is less than 10%.2 Cornell University refers to the mortality rate as being very low.10 And while cats can also catch canine influenza, there have been no cat deaths reported from the virus.2
Is there a vaccine for dog flu?
A bivalent canine influenza vaccine is available that works against both strains.2 Not every dog needs an influenza vaccine, but dogs that have frequent contact with other dogs would probably benefit the most. This includes dogs that frequent doggie daycare, kenneling facilities, dog shows, and groomers.
Vaccination may also be recommended for dogs who are at higher risk for severe illness due to underlying comorbidities like heart or respiratory issues.3 Some boarding facilities might even require the shot.
Vaccine timing and symptoms
The initial flu vaccine requires two injections, separated by two to four weeks, and then a booster every year.8 According to the American Veterinary Medical Association, dogs typically have mild side effects from an influenza vaccine, which can include lethargy, decreased appetite, some discomfort and sometimes mild respiratory symptoms such as sneezing or coughing.9
While the dog flu vaccination cannot completely prevent infection, it can greatly reduce the risk of infection and is believed to reduce the severity and duration of canine flu if infected.2 You'll want to consult your veterinarian to decide what is best for your dog.
The bottom line: Prevention is your best line of defense
The approaching human flu season is a good reminder to discuss canine flu with your veterinarian. This is especially important if your dog has any pre-existing health issues or is in frequent contact with other dogs, particularly in environments that increase the risk of infection. Fortunately, Pets Best insurance plans can help you afford the best treatment if your dog becomes ill. Optional routine care coverage also offers reimbursement for preventative treatments including the dog flu vaccine.
Terms and conditions apply. See policy for details.
Sources:
1Crawford PC : Canine Influenza Virus - Old and New. 4th International Society for Companion Animal Infectious Diseases Symposium 2016.
2"Canine Influenza." American Veterinary Medical Association, https://www.avma.org/resources-tools/animal-health-and-welfare/canine-influenza. Last accessed September 29, 2022.
3Ward, Ernest. "Canine Influenza: The Dog Flu." VCA Animal Hospitals, https://vcahospitals.com/know-your-pet/canine-influenza-the-dog-flu. Last accessed September 29, 2022.
4"Key Facts about Canine Influenza (Dog Flu)." Centers for Disease Control and Prevention, https://www.cdc.gov/flu/other/canine-flu/keyfacts.html. Last accessed September 29, 2022.
5Serological survey of canine H3N2, pandemic H1N1/09, and human seasonal H3N2 influenza viruses in cats in northern China, 2010-2014.Free Full-text Journals: Virol J. 2015; 12(0):50. Xuxiao Zhang, Ye Shen, Lijie Du et al
6King LG: Canine Influenza: Epidemiology, Clinical Disease, Diagnosis, Treatment, and Prevention. Western Vet Conference 2010
7"Can Dogs Get Sick From Humans?" Healthline, https://www.healthline.com/health/can-dogs-get-sick-from-humans. Last accessed September 29, 2022.
8Klein, Jerry, "Do Dogs Need a Flu Shot? Facts About the Canine Influenza Vaccine." AKC, September 28, 2021, https://www.akc.org/expert-advice/health/dog-flu-shot-canine-influenza/. Last accessed September 29, 2022.
9"What to Expect After Your Pet's Vaccination." AVMA, https://www.avma.org/resources-tools/pet-owners/petcare/what-expect-after-your-pets-vaccination. Last accessed September 29, 2022.
10"Canine Influenza Virus." Cornell University, https://www.vet.cornell.edu/animal-health-diagnostic-center/veterinary-support/disease-information/canine-influenza-virus. Last accessed September 29, 2022.