What is canine influenza (dog flu)?
Dog flu is a contagious respiratory disease in dogs caused by a specific Type A influenza virus referred to as a “canine influenza virus.” This is a disease of dogs, not of humans.

What is a canine influenza virus?
The “canine influenza virus” is an influenza A H3N8 influenza virus (not a human influenza virus) that was originally an equine (horse) influenza virus. This virus has spread to dogs and can now spread between dogs.

How long has canine influenza been around?
The H3N8 equine influenza 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. An investigation showed that this respiratory illness was caused by the equine influenza A H3N8 virus. Scientists believe that this virus jumped species (from horses to dogs) and has now adapted to cause illness in dogs and spread efficiently among dogs. This is now considered a new dog-specific lineage of H3N8. In September of 2005, this virus was identified by experts as “a newly emerging pathogen in the dog population” in the United States.

What are the symptoms of this infection in dogs?
The symptoms of this illness in dogs are cough, runny nose and fever, however, a small proportion of dogs can develop severe disease.

How serious is this infection in dogs?
The number of dogs infected with this disease that die is very small. Some dogs have asymptomatic infections (no symptoms), while some have severe infections. Severe illness is characterized by the onset of pneumonia. Although this is a relatively new cause of disease in dogs and nearly all dogs are susceptible to infection, about 80 percent of dogs will have a mild form of disease.

How does dog flu spread?
Canine influenza virus can be spread by direct contact with respiratory secretions from infected dogs, by contact with contaminated objects, and by people moving between infected and uninfected dogs. Therefore, 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.

Is there a test for canine influenza?
Testing to confirm canine influenza virus infection is available at veterinary diagnostic centers. The tests can be performed using respiratory secretions collected at the time of disease onset or using two blood samples; the first collected while the animal is sick and the second 2 to 3 weeks later.

How is canine influenza 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?
Yes, an approved vaccine is available.

What is the risk to humans from this virus?
To date, there is no evidence of transmission of canine influenza virus from dogs to people and there has not been a single reported case of human infection with the canine influenza virus. While this virus infects dogs and spreads between dogs, there is no evidence that this virus infects humans.

However, human infections with new influenza viruses (against which the human population has little immunity) would be concerning if they occurred. 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. Such a virus could represent a pandemic influenza threat. For this reason, CDC and its partners are monitoring the H3N8 influenza virus (as well as other animal influenza viruses) along with instances of possible human exposure to these viruses very closely. In general, however, canine influenza viruses are considered to pose a low threat to humans. As mentioned earlier, while these viruses are well established in horse and dog populations, there is no evidence of infection among humans with this virus.

My dog has a cough what should I do?
Schedule an appointment with your veterinarian so that 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.

With a new, highly contagious canine flu spreading, dogs that are coughing should be kept at home for up to two weeks, a scientist who first described the illness said yesterday.

The scientist, Dr. Cynda Crawford, an immunologist at the University of Florida College of Veterinary Medicine and an author of a report on the canine influenza being released today by the journal Science, spoke at a news conference sponsored by the Centers for Disease Control and Prevention.

The C.D.C., which is tracking the disease, issued no official recommendations. But Dr. Crawford urged pet owners to continue to walk healthy dogs, visit dog runs, use boarding kennels and otherwise let animals congregate. But, Dr. Crawford added, owners should "use common sense," including isolating dogs with any symptoms of respiratory disease for up to two weeks and alerting a veterinarian's office before taking in a sick dog for treatment.

Dr. Crawford, who was joined at the news conference by scientists at the C.D.C. and the Cornell University College of Veterinary Medicine who are studying the virus, said the flu seemed to kill 5 to 8 percent of the dogs it infected. But she emphasized that scientists did not "have all the answers" on fatality rates because the influenza strain was new and because it was hard to get accurate information about dog deaths. Last week, Dr. Crawford estimated the fatality rate at 1 to 10 percent. In the first outbreak she studied, at a greyhound track last year in Jacksonville, Fla., the flu killed about a third of the dogs with symptoms. But she said basing estimates on a single outbreak left "a false impression."

The flu initially mimics "kennel cough," a common disease usually caused by Bordetella bronchiseptica, a bacterium related to the one that causes whooping cough in children. About 80 percent of infected dogs develop a cough, nasal discharge and possibly a fever; a smaller number go on to develop pneumonia. The 20 percent of dogs with no symptoms are presumed to be contagious, Dr. Crawford said.

Dr. Ruben Donis, chief of molecular genetics for the influenza branch of the disease control agency, said the flu had jumped from horses to dogs, "a very rare event of considerable scientific interest." But, Dr. Donis said, "at this point, there is no reason to panic."

Although there has been speculation that the influenza could now jump to humans because dogs live more intimately with them than horses do, the H3N8 strain has been found in horses for over 40 years without ever causing a documented human case, he said. A vaccine for the canine flu is under development, he said; a vaccine for the equine version already exists.

It is unclear how widespread the disease is in pets around the country. The first outbreaks in kennels not connected to greyhound tracks were found in April, and cases among pets have been confirmed only in Florida, New York and Massachusetts. Dr. Edward J. Dubovi, chief virologist in Cornell's diagnostic laboratory in Ithaca, said he was testing samples from veterinarians in many states