February 12, 2023
Phil Good, DVMIntroduction
As the cold winds of winter begin to pick up, Emma, a devoted dog owner, noticed her furry friend exhibiting symptoms of what seemed like the flu. With a sinking feeling in her chest, she realized her dog, Luna, might not be immune to the seasonal ailments that affected humans. Determined to protect Luna and keep her in good health, Emma embarked on a quest to learn everything she could about the canine flu.
As the cold and flu season approaches, we all take measures to protect ourselves and our families from getting sick. But have you thought about protecting your family’s pet dog?
Canine influenza, or “Dog Flu,” is a real threat to pets nationwide. Recently there have been several high-profile outbreaks in major cities and small towns, leaving many pet owners scared for their pup’s safety. Every year, strains of flu viruses make their way around the world, infecting people and animals, and dogs can be particularly susceptible to these seasonal illnesses.
However, there are steps you can take to minimize the risk that your pup will contract the flu this winter. In this article, I will explain how to keep your dog healthy during the rest of the fall and all winter long.
Quick facts
- Dog flu is a contagious respiratory disease in dogs, caused by influenza A viruses H3N8 and H3N2. It’s not a stomach bug. (CDC)
- Most dogs get mild illness and recover. A small number develop pneumonia and need hospital care. (Merck Veterinary Manual)
- Risk to people is low, and there’s no evidence that dog-flu viruses regularly infect humans. (CDC, CDC Archive)
- A bivalent vaccine (protects against H3N2 + H3N8) reduces illness and shedding in at-risk dogs. (MSD Veterinary Manual)
What is canine influenza?
Canine influenza (often called “dog flu”) is a virus that infects a dog’s airways—nose, throat, and lungs. Two main strains circulate in the U.S.: H3N8 and H3N2. Both spread easily where dogs mix, like daycares, boarding, grooming, shelters, dog shows, and dog parks. (CDC, Cornell Vet School)
Cats can catch H3N2 from dogs during outbreaks, so keep sick dogs away from cats, too. (AVMA)
How does it spread?
Droplets and close contact: coughs, barks, sneezes.
Shared items: bowls, toys, leashes, crates, and hands or clothing of people moving between dogs.
- Dogs can start spreading the virus before they look sick. (CDC, Los Angeles County Public Health)
Timeline
- Incubation (time from exposure to signs): usually 2–3 days.
- Peak virus shedding: days 3–4.
Shedding lasts ~7 days for H3N8, but can last 21–24 days for H3N2—so isolation needs to be longer for H3N2. (Cornell Vet School)
Signs to watch for
Most dogs have signs like:
- Cough (dry or wet), sneezing, runny nose/eyes
- Tiredness, reduced appetite
- Fever (may be high)
A few dogs develop pneumonia: heavy breathing, blue gums, severe lethargy, or persistent high fever. These are emergencies. (Merck Veterinary Manual)
When to call your veterinarian now
Breathing is hard, fast, or noisy
Not eating or drinking, or vomiting repeatedly
Very young, very old, brachycephalic (short-nosed), pregnant, or immunocompromised pets
Symptoms lasting more than 2–3 days or quickly getting worse
How is dog flu diagnosed?
Vets cannot confirm dog flu by symptoms alone. The go-to test is a PCR swab from the nose or throat. Chest x-rays may be used if pneumonia is suspected. Testing early (first 4–5 days of illness) is best. (Today’s Veterinary Practice, AAHA, Cornell Vet School)
Treatment (what helps—and what doesn’t)
There’s no specific antiviral drug routinely used for dog flu. Care focuses on:
- Rest and hydration
- Nutrition (warm the meal if it boosts appetite, but the warmth itself doesn’t treat flu)
- Medications from your vet: cough suppressants, anti-inflammatories, or antibiotics only if there is a secondary bacterial infection or pneumonia
Avoid human cold medicines (like acetaminophen, ibuprofen, decongestants). Many are dangerous for pets. (Merck Veterinary Manual)
Home care and isolation
Isolate your dog from other dogs:
H3N8: at least 7 days after symptoms start
H3N2: 21 days after symptoms start (shedding can be longer) (Cornell Vet School, College of Veterinary Medicine)
Separate supplies: bowls, toys, bedding, crates, leashes.
Clean and disinfect: influenza is an enveloped virus and is easily killed with common disinfectants (follow label directions). Wash hands after handling the sick pet. (Shelter Medicine)
Keep cats away from dogs with suspected H3N2. (AVMA)
Vaccination: who needs it and how it works
- Who should get it? Dogs who mix with other dogs (daycare, boarding, grooming, parks, training classes, shows, shelters) are at higher risk. Many facilities require it. (Cornell Vet School)
- What to get? A bivalent vaccine (H3N2 + H3N8).
- Schedule: Two doses 2–4 weeks apart, then yearly boosters.
What it does: Lowers the chance of severe illness and reduces virus shedding; like human flu shots, it’s not 100% but it helps a lot. (MSD Veterinary Manual)
Myths vs. facts
“Dogs catch the human flu from people.”
Rare and not a driver of outbreaks. Dog-flu viruses are different. Risk to humans is low. (CDC, CDC Archive)
“Antibiotics cure dog flu.”
Antibiotics don’t kill viruses; vets use them only for secondary bacterial infections. (Merck Veterinary Manual)
“Humidifiers and supplements prevent dog flu.”
Clean air and good nutrition support recovery, but they don’t prevent or treat influenza infection. Focus on isolation, hygiene, and vaccination. (CDC, MSD Veterinary Manual)
“It’s just kennel cough.”
Kennel cough (now called CIRD—canine infectious respiratory disease) has many causes. Influenza is one of them, and it can look similar, which is why testing matters. (Merck Veterinary Manual)
Simple action plan if your dog might have flu
Call your veterinarian for advice and testing.
Isolate your dog from other dogs (and cats, if H3N2 is suspected).
Push fluids and rest; follow your vet’s treatment plan.
Clean shared surfaces and wash hands often.
Ask about vaccination for any dog that goes to social settings.
