Thursday, April 09, 2015

CDC Statement On Canine Influenza In Chicago

3D model generic Flu Virus – Credit CDC PHIL


# 9920



Up until a dozen years ago, most veterinarians would have told you that dogs are not generally susceptible to influenza viruses, but that notion changed in 2004 when we saw the jump of equine H3N8-like influenza to Florida greyhounds.


In 2008, an EID Journal article reported:


Influenza A Virus (H3N8) in Dogs with Respiratory Disease, Florida

Sunchai Payungporn*, P. Cynda Crawford†, Theodore S. Kouo*, Li-mei Chen*, Justine Pompey*, William L. Castleman†, Edward J. Dubovi‡, Jacqueline M. Katz*, and Ruben O. Donis*Comments to Author

In 2004, canine influenza virus subtype H3N8 emerged in greyhounds in the United States. Subsequent serologic evidence indicated virus circulation in dog breeds other than greyhounds, but the virus had not been isolated from affected animals. In 2005, we conducted virologic investigation of 7 nongreyhound dogs that died from respiratory disease in Florida and isolated influenza subtype H3N8 virus.

Antigenic and genetic analysis of A/canine/Jacksonville/2005 (H3N8) and A/canine/Miami/2005 (H3N8) found similarity to earlier isolates from greyhounds, which indicates that canine influenza viruses are not restricted to greyhounds. The hemagglutinin contained 5 conserved amino acid differences that distinguish canine from equine lineages. The antigenic homogeneity of the canine viruses suggests that measurable antigenic drift has not yet occurred. Continued surveillance and antigenic analyses should monitor possible emergence of antigenic variants of canine influenza virus.


Like its equine counterpart (which has been around at least a half century) - canine H3N8 has not been shown to infect humans. The CDC considers this a dog-specific lineage of H3N8.


North American canine H3N8 should not be confused with a similarly named avian Mammalian Adapted H3N8 In Seals, Equine H3N8, or the more recently emerged canine H3N2 virus which is spreading in dogs and cats across parts of Asia (see Korea: Interspecies Transmission of Canine H3N2).


Over the past few weeks there has been an unusually large outbreak of canine H3N8 in and around the Chicago area, and yesterday the CDC posted the following statement.


Canine Influenza (Dog Flu) Outbreak in Chicago Area

April 8, 2015 – CDC is aware of reports of a canine influenza (dog flu) outbreak in the Chicago area. Dog flu is a contagious respiratory disease in dogs that does not cause illness in humans. A vaccine against this disease in dogs has been available since 2009. CDC recommends that people concerned about dog flu speak to their veterinarian.

Signs of dog flu infection include cough, runny nose and fever, but not all dogs will exhibit signs. The severity of illness associated with dog flu can range from no signs to severe illness resulting in pneumonia and sometimes death. Tests are available to determine if a dog has been infected, and your veterinarian can tell you if testing is appropriate. You and your veterinarian can also discuss whether vaccinating your dog against canine influenza is indicated.

Dog flu is caused by an influenza A (H3N8) virus that is closely related to an influenza virus found in horses for over 40 years. Experts believe this horse influenza virus changed in a way that allowed it to infect dogs, and the first dog flu infections caused by these viruses were reported in 2004, initially in greyhounds. This virus is now considered a dog-specific lineage of influenza A (H3N8) virus. Almost all dogs can be susceptible to infection, and illness tends to spread among dogs housed in kennels and shelters.

To date, there is no evidence of transmission of dog flu from dogs to people and there has not been a single reported case of human infection with the canine influenza virus.

For more information on dog flu, please visit:

While this strain of canine influenza is not currently viewed as having zoonotic properties, we’ve looked at studies on other canine-acquired influenza viruses – particularly in Asia – that have put dogs on the radar as a possible `mixing vessel’ for influenza reassortment.


A few recent blogs include:


Virology J: Human-like H3N2 Influenza Viruses In Dogs - Guangxi, China

China: Avian-Origin Canine H3N2 Prevalence In Farmed Dogs

MAFRA: H5N8 Antibodies Detected In South Korean Dogs (Again)

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