Canine influenza (also known as dog flu) is a contagious respiratory disease in dogs caused by specific Type A influenza viruses known to infect dogs. These are called "canine influenza viruses”. Dog flu is a disease of dogs. No human infections with canine influenza have ever been reported.
There are two different influenza A dog flu viruses: H3N8 virus and H3N2 virus. Due to influenza viruses constantly changing, it is possible for a virus to change so that it could infect humans and spread easily between humans. For this reason, CDC and its partners are monitoring the canine influenza H3N8 and H3N2 viruses (as well as other animal influenza viruses) closely.
The signs of this illness in dogs are cough, discharge from nose or eyes, lethargy, decreased appetite, and fever, however not all dogs will show signs of illness. The onset of symptoms is usually 2-4 days, but can last up to 30 days. The severity of illness associated with canine flu in dogs can range from no signs to severe illness resulting in pneumonia and sometimes death. The percentage of dogs infected with this disease that die is very small. Some dogs have asymptomatic infections (no signs of illness), while some have severe infections. Severe illness is characterized by the onset of pneumonia. This is a relatively new cause of disease in dogs and nearly all dogs are susceptible to infection.
Testing to confirm canine influenza virus infection in dogs is available. Your veterinarian can tell you if testing is appropriate. Treatment largely consists of supportive care. This helps the dog mount an immune response. In the milder form of the disease, this care may include medication to make your dog more comfortable and fluids to ensure that your dog remains well hydrated. Your veterinarian may prescribe broad-spectrum antibiotics if a secondary bacterial infection is suspected.
There is an approved vaccine to protect dogs against canine influenza A H3N8 available in the United States. It is unknown at this time whether this vaccine will protect against the H3N2 canine flu virus. It is recommended that all dogs in a social environment such as daycare, boarding, grooming, or dog parks, get vaccinated. The vaccine is a two series treatment about 2-4 weeks apart and boostered yearly. Most facilities are already requiring the vaccine.
The 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. Proper thorough hand washing and disinfection of clothing and surfaces should be done when moving between infected to uninfected dogs.
More information on canine influenza can be found in the following articles:
Media Briefing on Canine Influenza. September 25, 2005. http://www.cdc.gov/media/transcripts/t050926.htm.
Update on Canine Influenza (Dog Flu) Outbreak Reported in Chicago Area. April 13, 2015. http://www.cdc.gov/flu/news/canine-influenza-update.htm.
Influenza A Virus (H3N8) in Dogs with Respiratory Disease, Florida. Volume 14, Number 6 – June 2008.