Everything You Need to Know About Dog Flu

Almost every dog is at risk of this highly contagious respiratory virus.



Clinical Signs





Dog Flu is an emerging threat to all dogs.

Dog Flu is a relatively new disease which can be caused by two different canine influenza viruses. Just like human flu is among humans, Dog Flu is highly contagious among dogs. In fact, unless a dog has already had the illness and recovered, almost every dog exposed to the virus will become infected. Two different strains of canine influenza virus have been isolated in the US. Canine influenza virus H3N8 was first reported in 2003, and canine influenza virus H3N2 emerged in March 2015. These strains are not related. Therefore, dogs at risk should be vaccinated against both strains.2 This is because the viruses are relatively new, and dogs have no natural immunity to it. Nobivac® Canine Flu H3N8 was the first vaccine for Dog Flu and still is highly effective against this strain. It has been clinically proven to significantly reduce the severity of influenza and the length of time that a dog is sick.33 The bivalent flu vaccine was licensed in October 2016 and is the first bivalent Dog Flu vaccine. This vaccine aids in the control of disease associated with Canine Influenza Virus H3N8 and H3N2 infection.

Canine influenza virus (CIV H3N8) has been confirmed in dogs across 43 states and the District of Columbia. In March 2015, a different canine influenza virus, CIV H3N2, caused an outbreak of canine influenza in Chicago. Within 5 months this virus spread to 23 states.1 And because most dogs are naive to the virus, virtually every naive dog exposed will become infected.2 Clinical signs associated with CIV can be confused with canine cough making accurate diagnosis difficult. Nobivac® Canine Flu H3N8 — a killed virus vaccine from Merck Animal Health — was the first vaccine fully licensed by the USDA for canine influenza. It significantly decreases clinical signs of disease and reduces viral shedding.

This website offers important information about Dog Flu, including information on diagnosis, treatment, and prevention. If you have specific questions about canine influenza or would like additional information about Nobivac® Canine Flu Bivalent simply contact your veterianrian or our Merck Animal Health professionals.

Dog outside
Dog at the vet

AAHA Kennel and Boarding Safety Recommendations (Winter 2017)

The American Animal Hospital Association (AAHA)'s award-winning Trends Magazine has published Kennel and Boarding Safety Recommendations in the February 2017 issue. The recommendations are designed to help pet professionals prevent the spread of infectious disease within their businesses, including kennels, veterinary facilities, doggie daycares, dog walkers, groomers and training facilities. These recommendations are the result of a veterinary and pet business expert roundtable sponsored by Merck Animal Health, which was initiated in response to the ever-evolving disease trends impacting the industry, including the canine influenza H3N2 outbreak. The guidance document emphasizes the importance of disease prevention, vaccination requirements, sanitation and isolation procedures, and having an issues management and communication plan in place in the event of an infectious disease outbreak, as well as the importance of managing legal issues to protect the reputation and viability of a pet business. Learn More

Between 80 to 90% will develop clinical infection
Up to 20% of dogs

with Dog Flu will develop a more severe systemic form of canine influenza that manifests with a high fever (104-106°F) and pneumonia

About 10 to 20% of dogs will contract the infection but not show clinical signs

It is important to note that dogs that do not show clinical signs can still pass the infection to other dogs. The mortality rate of canine influenza has been reported to range from 1% to 8% in puppies and older dogs.2 Serology can be performed to confirm a diagnosis of CIV infection; however, samples must be sent out, so this diagnostic test does not help acute management.8

There is no treatment specifically for Dog Flu; treatment consists of supportive therapy. Intravenous fluids may be helpful. Antibiotics may be indicated in the case of secondary bacterial infection, with selection guided by culture and sensitivity testing.2,6

The pattern of a sudden increase in the prevalence of acute respiratory disease, severity of illness, or a lack of response to antibiotic therapy is one of the first warning signs of a CIV outbreak. It is important to recognize this pattern so that appropriate isolation and other precautions can be taken to minimize the spread of this highly contagious virus. In addition, a veterinarian should be consulted to ensure that appropriate treatment is implemented.

As with any infectious disease outbreak, management of canine influenza requires breaking the cycle of transmission among dogs that are infected and those that are exposed through:

  • Early recognition, treatment, and isolation of infected or potentially infected dogs
  • Environmental control procedures
  • Education of veterinary professionals, kennel owners, shelter managers, and dog owners
  • Vaccination

Nobivac® Canine Flu Bivalent just recently was launched as an aid in the control of disease associated with canine influenza H3N8 and H3N2 infection. Canine influenza virus H3N8 is of equine origin and canine influenza virus H3N2 is of avian origin. These viruses are not related. Therefore, dogs at risk should be vaccinated against both strains.

2017 AAHA Canine Lifestyle-Based Calculator

Every pet has different personalities, and environments they find themselves in. This is why vaccination needs can differ between dogs and locations. To help veterinary clinics stay on top of the newest canine guidelines, AAHA has released the most updated information online. Find out more about current vaccinations, and learn which vaccinations would be best for each dog, with the Lifestyle-based Vaccine Calculator.

Dog outside

1. Syndromic surveillance data of Cynda Crawford, DVM, PhD, University of Florida; Edward Dubovi, PhD, Cornell University; Sanjay Kapill, DVM, PhD, ACVIM, Oklahoma State University; and IDEXX Laboratories. May 2017.

2. Crawford C, Spindel M. Canine influenza. In: Miller L, Hurley K, eds. Infectious Disease Management in Animal Shelters. Ames, IA: Wiley-Blackwell; 2009:173-180.

6. Canine influenza. The Center for Food Security & Public Health. College of Veterinary Medicine, Iowa State University. Available at: http://www.cfsph.iastate.edu/Factsheets/pdfs/canine_influenza.pdf. Updated June 2014. Accessed December 9, 2015.

8. Information sheet: Canine influenza, Updated July 2015. UC Davis Koret Shelter Medicine Program Website. Available at: http://www.sheltermedicine.com/library/canine-influenza. Accessed December 9, 2015.

33. Deshpande MS, Jirjis FF, Tubbs AL, et al. Evaluation of the efficacy of a canine influenza virus (H3N8) vaccine in dogs following experimental challenge. Vet Ther. 2009;10(3):103-112.


Read common questions about Dog Flu strains, spread and vaccinations.

About Dog Flu

Read more about Dog Flu origins, treatment, symptoms and prevention.

Locate a Veterinarian

Speak to a pet professional about vaccination and other preventive measures.