Midwest Canine Influenza Outbreak: A New Virus Within the United States by Nancy Kay, DVM
Photo Credit: Steven Turville
If you keep tabs on dog-related news, you’re probably already aware of the recent outbreak of canine influenza in the Midwest. Chicago appears to be at the epicenter of the epidemic.
The first dogs affected by this virus were observed in mid-March of this year. Since then, more than 1,000 known cases have been reported in and around Chicago, and there have even been a few deaths.
New virus within the United States
Until a week ago, the virus responsible for this canine influenza outbreak was thought to be H398, a strain of Influenza A that has been present in the United States for some time. Cornell University (thumbs up to my alma mater) recently reported that scientists there have isolated a brand new influenza virus from affected dogs in the Midwest. This virus, referred to as H3N2, is closely related to strains of influenza affecting dog populations in South Korea and China. H3N2 is now making its debut appearance within the United States. How the virus was introduced here is anyone’s guess.
Dogs living within the United States have no natural protection against H3N2 because their immune systems have never been exposed to it before. For this reason, it will remain highly contagious until canine populations develop immunity, either through natural infection or vaccination.
The contagious stage of canine influenza begins a few days before symptoms arise. In other words, the healthy-appearing pup at the dog park or doggie daycare center may be on the verge of developing viral symptoms. Spread of the disease occurs via respiratory secretions (discharge from nose, mouth, and eyes). Both dogs and cats are susceptible to the H3N2 virus. It is not transmissible to humans.
The symptoms most commonly associated with influenza virus include: high fever, loss of appetite, coughing, nasal discharge, and lethargy. In the best-case scenario, an infected dog may show only mild symptoms or none at all. Worst-case scenario, pneumonia may develop. Pneumonia was the likely cause of death in five dogs who have reportedly succumbed to this disease.
Many infectious bacterial and viral diseases are capable of producing the symptoms described above. Knowing that H3N2 is the culprit requires specialized testing performed on a mouth or nose swab. Cornell reports that the development of a blood test capable of diagnosing this disease is in the works.
Treatment of influenza ideally involves supportive and symptomatic care until the dog’s immune system wins the battle against the virus (requires approximately two weeks for most dogs). Therapy may include supplemental fluids, special diets to entice appetite, anti-inflammatory medications, and cough suppressants. Antibiotics may be prescribed to prevent secondary bacterial infection.
If evidence of pneumonia is present, much more intensive therapy is indicated and may include hospitalization for intravenous fluids and antibiotics, supplemental oxygen, and 24-hour monitoring by a veterinarian.
At this time, it is not known if the vaccine currently available to prevent H3N8 is also protective against the newer H3N2 strain. There may be some cross over protection, but just how much is uncertain. I suspect that updated information about the effectiveness of the current vaccine and/or development of a new vaccine will be forthcoming in the near future. For now, I recommend discussing use of the current influenza vaccine with your veterinarian.
If you live in or around Chicago, or if you learn that influenza cases are beginning to pop up in your neck of the woods, know that the very best protection involves keeping your dog away from popular, public, canine venues such as dog parks, boarding kennels, grooming parlors, pet stores, and doggie daycare facilities.
Please know that there is no cause for panic. The vast majority of dogs affected by this new strain of influenza fully recover. Talk with your veterinarian about the incidence of canine influenza in your locale to help determine the level of concern for your dogs.