Frequently Asked Questions

In March 2015, veterinarians in and around the Chicago area began to notice an increase in the number of dogs presented to their clinics for respiratory illness. The dogs had signs involving the respiratory system including coughing, nasal and ocular discharge, and lethargy. Initial diagnostic testing was found to be inconclusive. In order to help support the veterinary community, Merck Animal Health sponsored a diagnostic sampling program with Chicago area veterinary clinics.

In this program, nasal and pharyngeal swabs were taken from sick dogs to help identify the causative agent. Samples were forwarded to the New York State Veterinary Diagnostic Laboratory at Cornell University. Over 350 samples were finalized between March 10 and April 23, 2015, and of these, 198 dogs tested positive for Dog Flu, or canine influenza. At first, it was presumed that the Dog Flu strain was H3N8, however, after further evaluation by Cornell and the University of Wisconsin, the strain has been identified as H3N2. This is the first time this strain of Canine Influenza has been found in North America. Further testing has shown that this form of H3N2 is nearly identical to H3N2 found in dogs in Korea.

Other pathogens are commonly found when testing for dog flu. They include parainfluenza, adenovirus type 2, bordetella, pneumovirus, and respiratory coronavirus. Vaccines are available for protection of parainfluenza, adenovirus, and bordetella. There are no vaccines commercially available in the United States for pneumovirus or respiratory coronavirus.

Both H3N8 and H3N2 are influenza viruses that cause respiratory infections in dogs. H3N8 was first discovered in Florida in 2004 and is of equine influenza origin. Avian origin H3N2 influenza virus was found in China in 2006 and in Korea. While H3N8 is shed by infected dogs for 5 days, H3N2 can be shed intermittently for up to 24 days.

To date, there is no evidence of transmission of canine influenza viruses (H3N2 or H3N8) from dogs to people.

H3N2 can affect cats but not H3N8.

According to data from cases of H3N2 infection in cats in Asia, signs seen in cats are similar to those seen in dogs and include lethargy, coughing, fever, sneezing, and potentially pneumonia.

Clinical flu virus symptoms in dogs include coughing, fever, and lethargy. More severe signs, including pneumonia, can be seen in more severe cases. Necropsy reports from dogs with confirmed H3N2 infection revealed severe, acute, locally extensive necrohemorrhagic interstitial pneumonia with epithelial necrosis.

It is not known how the virus was brought into the United States. The virus has been identified as related to the Korean strain of H3N2.

According to clinical data studies (currently under peer review) at the University of Wisconsin, this new strain of Dog Flu is likely has a longer, up to 24 days, contagious period--making it more of a concern.

Both the scientific literature and what has been seen during the outbreaks suggests that Dog Flu is highly infectious. The virus spreads rapidly, especially at boarding facilities, groomers, doggy day cares, dog parks and other spots where dogs co-mingle. Dog Flu can be spread by direct contact with respiratory discharge from infected dogs, through the air via a cough or sneeze, and by contact with contaminated objects such as dog bowls and clothing, or by people moving between infected and uninfected dogs. Dog owners whose dogs are coughing or showing other signs of respiratory disease should not participate in activities or bring their dogs to facilities where other dogs can be exposed to the virus.

The virus spreads rapidly, especially at boarding facilities, groomers, doggy day cares, dog parks and other spots where dogs co-mingle.

The Dog Flu virus can be spread by direct contact with respiratory discharge from infected dogs, through the air via a cough or sneeze, and by contact with contaminated objects such as dog bowls and clothing, or by people moving between infected and uninfected dogs.

Dog owners whose dogs are coughing or showing other signs of respiratory disease should not participate in activities or bring their dogs to facilities where other dogs can be exposed to the virus.

Clothing, equipment, surfaces, and hands should be cleaned and disinfected after exposure to dogs showing signs of respiratory disease.

Contact your veterinarian if your dog has the following symptoms:

• Coughing
• Discharge from the nose or eyes
• Loss of appetite
• Lethargy/lack of energy

Treatment consists mainly of supportive care, such as fluids and medication to help a dog be more comfortable. With severe illness, hospitalization is necessary.