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everything you need to know about the dog flu outbreak

Update: May 31, 2017: Health officials confirm seven of dog flu cases in Florida for the first time.

Update: May 3, 2016: Cats confirmed to be infected with H3N2 canine influenza in Indiana. There is currently no vaccine against H3N2 in cats.

Update: January 22, 2016: The first two H3N2 cases have been documented in Washington state.

Update: January 22, 2016: Dog flu confirmed in Texas.

Update: January 16, 2016: There are two new vaccines for H3N2, produced by Zoetis and Merck, in addition to the vaccine for H3N8 canine influenza. There is no evidence the existing H3N8 vaccine will provide protection for the new H3N2 strain or vice versa.

The recent canine influenza outbreak that spread from the Midwest to at least 20 states has been identified as a new viral strain from Asia. Veterinary researchers from Cornell University and the University of Wisconsin Veterinary Diagnostic Laboratory have determined a canine respiratory virus found in China and South Korea, H3N2, is to blame for nearly 2,000 reported cases in the U.S. H3N2 is not known to be contagious to humans, although cats have been proven to be at risk for contracting the respiratory infection. This is the first time the Asian virus has been identified in the U.S.  


The canine influenza outbreak was originally thought to be the result of H3N8 or canine influenza virus (CIV), a highly contagious canine respiratory virus first observed in Florida racing Greyhounds in 2004. The more recent Asian strain, H3N2, was initially identified in 2006 in Asia. H3N2 originated in avian species and apparently mutated to become infectious to dogs, cats and ferrets. Since 2006, H3N2 has been identified throughout China and South Korea.


signs & symptoms

Dogs and cats infected with H3N2 canine influenza have clinical signs similar to CIV: high fever, loss of appetite, coughing, nasal discharge and lethargy. Cats have been reported to experience runny noses, severe congestion, excessive salivation and lethargy. There is a rapid, specific viral test available for H3N2 canine influenza in both dogs and cats. Based on similar viruses, the incubation period is approximately two to three days, clinical signs last five to seven days and an infected animal may be contagious for up to 21 days after clinical signs develop.



We don’t know how this new strain of canine influenza arrived in the U.S. It is suspected that a dog harboring the virus was imported, although this has yet to be confirmed. Because this is a relatively new infection, we don’t fully understand the transmission and pathogenicity of H3N2 canine influenza virus.


what to do if you think your dog or cat has H3N2

If your dog or cat displays any symptoms of respiratory illness, notify your veterinarian at once. H3N2 is highly contagious; avoid contact with other pets if your dog or cat becomes ill, especially if you live in an area with reported H3N2. When CIV first presented in 2004-2005, U.S. veterinarians took great efforts to quarantine any dogs with fevers, coughing and nasal discharge from other pets. These aggressive medical countermeasures helped prevent a widespread epidemic.


It is important to notify your veterinarian about any nasal or respiratory symptoms before taking your pet to the clinic. Your pet will be immediately escorted to a separate clinic area and handled with proper infectious disease protocols to help prevent further spread.  


how to protect your pet

If you live in an area identified with a CIV or H3N2 outbreak, minimize contact with other dogs or cats. Dog parks, lakes or beaches, kennels, boarding facilities, groomers and doggie daycare services need to be carefully supervised if you choose to take your pet. In outbreak areas, it is advised to vaccinate your dog against both CIV (H3N8) and H3N2 viruses. There is no vaccine for cats to protect against CIV or H3N2 at this time.


H3N2 Asian canine influenza appears to be more easily spread and may be shed for a longer period than CIV, up to 3 weeks or more. This may explain how quickly and widespread the Asian H3N2 outbreak has been in the U.S. The fact that cats can also contract and spread the virus makes it even more worrying. Be exceptionally cautious if your dog or cat develops a fever, coughing or nasal discharge.


Here are five keys to help prevent the spread of H3N2 influenza:


  1. Vaccinate dogs when appropriate against both CIV (H3N8) and H3N2. If you live in area or are travelling to a region with a known CIV or H3N2 outbreak, consider vaccinating your dogs immediately. If you do not know if CIV or H3N2 is in your area, contact your veterinarian.
  2. Limit dog-to-dog direct contact, especially nose-to-mouth contact.
  3. Basic washing and bathing with soap and water seem effective at inactivating the virus.
  4. H3N2 virus appears to survive in the environment for 24 to 48 hours. Avoid areas with known exposure to H3N2 for at least two days. Infected pets should be quarantined for at least 21 days.
  5. If you handle a sick dog or cat, wash your hands and change clothes before contacting other animals.


The good news is that H3N2 appears to have a low mortality rate. No cat fatalities and only a few dog deaths have been attributed to this new canine influenza virus. Because we still don’t have a complete understanding of the H3N2 virus, it’s imperative to keep in mind that both CIV and H3N2 may lead to life-threatening pneumonia or serious respiratory illness. In older pets or those with underlying disease, even moderate respiratory disease can be fatal.  


H3N2 is a significant animal influenza virus that must be closely monitored by all pet owners. There continue to be critical scientific and medical questions we don’t have answers for yet. Viruses can mutate quickly and recommendations change dramatically in little time. Take precautions with other dogs or cats, wash your hands and bathe your dog frequently and contact your veterinarian immediately if your pet develops any signs of respiratory illness. 

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Posted by Petplan
on July 02 2015 08:19

The states that have recorded case of dog flu are as follows, as detailed by the Washington Post: Illinois, California, Alabama, New York, Wisconsin, Michigan, Texas, Massachusetts, Iowa, New Jersey, Indiana, and most recently, Georgia.

Posted by Diana Migchelbrink
on July 01 2015 18:49

Great article. Where can we find which states have seen cases?

Posted by Patricia Michko
on July 01 2015 16:11

good article, although you did not mention the 12 states the virus has spread to. please respond with a list of states

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