H3N2 Dog Flu Hits Arizona

H3N2 dog flu has come to Arizona.  In 2015, a new strain of canine influenza hit the Midwest sickening more than 1,000 dogs.  At first, the outbreak was attributed to Influenza A H3N8, a virus that was first observed in the United States in 2004. But further testing by researchers at the University of Wisconsin and Cornell University identified a new virus, H3N2. This avian virus was first found in 2007 in Korean dogs.  The H3N2 canine flue virus has also infected cats. So far, this influenza has not spread to humans. The virus spread across the United States until it finally came to Arizona. Now, two years later, two dogs at Maricopa County Animal Care and Control tested positive for the virus. Both are responding well to treatment.

Clinical signs range from mild malaise to anorexia, coughing, fever and a runny nose to severe pneumonia. Coughing lasts 10 to 30 days and fevers range from 104 to 106. The normal range for dogs and cats is 100 to 102.5. Deaths are rare but seen most often in brachycephalic breeds such as Shit tzus, Pekinese and pugs. Treatment is supportive as there is currently no cure available. Severely affected dogs and cats are placed in hospital isolation wards and treated with fluids, antibiotics and nebulization. The goal is to prevent a secondary bacterial pneumonia which can be life-threatening.

Since no specific treatment is available for this virus, prevention is the key to protecting both dogs and cats. I recommend vaccinating all brachycephalic breeds of dogs, immune suppressed and dogs who frequent dog parks, pet stores, boarding facilities and shelters. Since this is a new virus, dogs do not posses a natural immunity against it. There are two types of vaccines available for canine flu, one for H3N8 and one for H3N2. It is important to get the H3N2 vaccine because the H3N8 does not cross protect.  Take precautions to avoid accidental transfer of the virus from sick animals to your pets. Disinfect clothing, equipment and hands after interacting with other animals.


-Brooks, Wendy. “Canine Influenza (H3N8)”. The Pet Health Library, VIN, Published 10/24/2005, Reviewed 4/30/2014.


-‘Key Facts about Canine Influenza (Dog Flu)’. Centers for Disease Control and Prevention.

-Rishniw, Mark. ‘Canine Influenz’. VIN: Veterinary Partner, published 04/17/2015, reviewed and revised, 06/19/2017.

-Schwartz, Joe. “Midwest Canine Influenza outbreak caused by new strain of virus”. Mediarelations.cornell.edu. April 12, 2015.



Published by kristennelsondvm

Dr. Kristen Nelson grew up on a farm in Watertown, Minn., where she developed a deep love for animals of all kinds. She received a Doctor of Veterinary Medicine degree from the University of Minnesota, College of Veterinary Medicine. Kris then completed a small-animal internship at the prestigious Animal Medical Center in New York City. In addition to writing and speaking, she cares for small and exotic animals in Scottsdale, Az. Dr. Nelson is widely quoted in the media. Her credits include Ladies’ Home Journal, USA TODAY, the Los Angeles Times and numerous radio and television interviews. Dr. Nelson has written two books, Coated With Fur: A Vet’s Life and Coated With Fur: A Blind Cat’s Love. Kris and her husband Steve share their home with rescued cats, birds and a dog.