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: one is an H3N8
virus and the other is an H3N2 virus.
Can canine influenza viruses infect humans?
To date, there is no evidence of transmission of canine
influenza viruses from dogs to people and there has not been a single reported
case of human infection with a canine influenza virus.
However, influenza viruses are constantly changing and it
is possible for a virus to change so that it could infect humans and spread
easily between humans. Human infections with new influenza viruses (against
which the human population has little immunity) are concerning when they occur.
Such viruses could present pandemic influenza threats. For this reason, CDC and
its partners are monitoring the canine influenza H3N8 and H3N2 viruses (as well
as other animal influenza viruses) closely. In general, canine influenza
viruses are considered to pose a low threat to humans.
Where did canine influenza viruses come from and how long
has it been around?
Canine influenza H3N8 virus originated in horses, has
spread to dogs, and can now spread between dogs. The H3N8 equine influenza
(horse flu) virus has been known to exist in horses for more than 40 years. In
2004, however, cases of an unknown respiratory illness in dogs (initially
greyhounds) were reported in the United States. An investigation showed that
this respiratory illness was caused by the equine influenza A H3N8 virus.
Scientists believe this virus jumped species (from horses to dogs) and has
adapted to cause illness in dogs and spread among dogs, especially those housed
in kennels and shelters. This is now considered a dog-specific H3N8 virus. In
September 2005, this virus was identified by experts as a "newly emerging
pathogen in the dog population" in the United States.
The H3N2 canine influenza virus is an avian flu virus that
adapted to infect dogs. This virus is different from human seasonal H3N2
viruses. Canine influenza A H3N2 virus was first detected in dogs in South
Korea in 2007. This virus seems to have been an avian influenza virus that
adapted to infect dogs and has since been reported in China and Thailand. H3N2
canine influenza has reportedly infected some cats as well as dogs. It was
first detected in the United States in April 2015. The canine H3N2 virus is
genetically different from human seasonal H3N2 viruses. It is not known how
canine H3N2 virus was introduced into the United States.
What are signs of canine influenza infection in dogs?
The signs of this illness in dogs are cough, runny nose,
and fever, but not all dogs will show signs of illness. The severity of illness
associated with canine flu in dogs can range from no signs to severe illness resulting
in pneumonia and sometimes death.
How serious is canine influenza infection in dogs?
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.
How is canine influenza spread?
Almost all dogs are susceptible to canine flu infection,
and illness tends to spread among dogs housed in kennels and shelters. Canine
flu can spread to other dogs by direct contact with aerosolized respiratory
secretions (coughing and sneezing) from infected dogs, by uninfected dogs
coming into contact with contaminated objects, and by moving contaminated
objects or materials between infected and uninfected dogs. Therefore, dog
owners whose dogs are coughing or showing other signs of respiratory disease
should not expose their dog to other dogs. Clothing, equipment, surfaces, and
hands should be cleaned and disinfected after exposure to dogs showing signs of
respiratory disease.
Is there a test for canine influenza?
Testing to confirm canine influenza virus infection in dogs
is available. Your veterinarian can tell you if testing is appropriate.
How is canine influenza infection in dogs treated?
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. Broad spectrum antibiotics may be
prescribed by your veterinarian if a secondary bacterial infection is
suspected.
Is there a vaccine for canine influenza?
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.
My dog has a cough. What should I do?
Schedule an appointment with your veterinarian so they can
evaluate your dog and recommend an appropriate course of treatment.
Where can I find more information on canine influenza
virus?
More information on canine influenza in pet dogs can be
found in this article: Influenza A Virus (H3N8) in Dogs with Respiratory
Disease, Florida in Emerging Infectious Diseases journal, the AVMA website, and
this update on the April 2015 Chicago H3N2 canine influenza outbreak.
References
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.
http://wwwnc.cdc.gov/eid/article/14/6/07-1270_article.
Canine influenza.
https://www.avma.org/KB/Resources/Reference/Pages/Canine-Influenza-Backgrounder.aspx
