Title: Canine influenza

{{Short description|Influenza occurring in canines}}
{{cs1 config|name-list-style=vanc}}
{{Flu}}
'''Canine influenza''' ('''dog flu''') is [[influenza]] occurring in [[Canidae|canine]] animals. Canine influenza is caused by varieties of [[influenzavirus A]], such as [[equine influenza]] virus [[Influenza A virus subtype H3N8|H3N8]], which was discovered to cause disease in canines in 2004.&lt;ref&gt;{{Cite web |title=Canine influenza |url=https://www.avma.org/resources-tools/animal-health-and-welfare/canine-influenza |access-date=2023-09-14 |website=American Veterinary Medical Association |language=en}}&lt;/ref&gt;  Because of the lack of previous exposure to this virus, dogs have no natural [[Immunity (medical)|immunity]] to it.  Therefore, the disease is rapidly transmitted between individual dogs. Canine influenza may be [[endemic (epidemiology)|endemic]] in some regional dog populations of the United States.  It is a disease with a high [[morbidity]] (incidence of symptoms) but a low [[Mortality rate|incidence of death]].&lt;ref name=CDC/&gt;

A newer form was identified in Asia during the 2000s and has since caused outbreaks in the US as well. It is a mutation of [[H3N2]] that adapted from its [[avian influenza]] origins. Vaccines have been developed for both strains.

The two strains of [[Influenza A virus|Type A influenza virus]] found in canines are A(H3N2) and A(H3N8). Over time, there has been a discovery of sources of transmissions, identification of specific symptoms and the creation of vaccines.&lt;ref name=&quot;:03&quot;&gt;{{Cite web |date=2023-08-29 |title=Key Facts about Canine Influenza (Dog Flu) {{!}} Seasonal Influenza (Flu) {{!}} CDC |url=https://www.cdc.gov/flu/other/canine-flu/keyfacts.html |access-date=2023-09-28 |website=www.cdc.gov |language=en-us}}&lt;/ref&gt;

==History==
The highly contagious equine influenza A virus subtype H3N8 was found to have been the cause of [[Greyhound]] race dog fatalities from a respiratory illness at a [[Florida]] racetrack in January 2004. The exposure and transfer apparently occurred at [[horse-racing]] tracks, where [[dog racing]] had also occurred.  This was the first evidence of an influenza A virus causing disease in dogs.  However, [[Blood plasma|serum]] collected from racing Greyhounds between 1984 and 2004 and tested for canine influenza virus (CIV) in 2007 had positive tests going as far back as 1999.  CIV possibly caused some of the respiratory disease outbreaks at tracks between 1999 and 2003.&lt;ref name=VF/&gt;

H3N8 was also responsible for a major dog-flu outbreak in [[New York (state)|New York]] state in all breeds of dogs. From January to May 2005, outbreaks occurred at 20 racetracks in 10 states ([[Arizona]], [[Arkansas]], [[Colorado]], Florida, [[Iowa]], [[Kansas]], [[Massachusetts]], [[Rhode Island]], [[Texas]], and [[West Virginia]]).&lt;ref&gt;[http://www.medicalnewstoday.com/medicalnews.php?newsid=31284 Article 31284], Medical News Today referencing September 26 issue of ''Science Express'' (Vol. 309, No. 5743).&lt;/ref&gt;  As of August 2006, dog flu has been confirmed in 22 U.S. states, including pet dogs in Wyoming, California, Connecticut, Delaware, and Hawaii.&lt;ref name=DVM&gt;{{cite journal | last = Tremayne | first = Jessica | title = Canine flu confirmed in 22 states | journal = DVM | pages = 1, 66–67 |date=August 2006 }}&lt;/ref&gt;  Three areas in the United States may now be considered endemic for CIV due to continuous waves of cases: New York, southern Florida, and northern Colorado/southern Wyoming.&lt;ref name=Yin2007&gt;{{cite journal | last = Yin | first = Sophia | title = Managing canine influenza virus | journal = Veterinary Forum | volume = 24 | issue = 9 | pages = 40–41 | publisher = Veterinary Learning Systems | date = September 2007 }}&lt;/ref&gt;  No evidence shows the virus can be transferred to people, cats, or other species.&lt;ref&gt;{{cite web | last = Crawford | first = C |author2=Dubovi EJ |author3=Donis RO |author4=Castleman WL |author5=Gibbs EPJ |author6=Hill RC |author7=Katz JM |author8=Ferro P |author9=Anderson TC   | title = Canine Influenza Virus Infection | work = Proceedings of the North American Veterinary Conference | year = 2006 | url = http://www.ivis.org/proceedings/navc/2006/SAE/218.asp?LA=1 | access-date = 2007-04-21 }}&lt;/ref&gt;

[[H5N1]] ([[avian influenza]]) was also shown to cause death in one dog in [[Thailand]], following ingestion of an infected [[duck]].&lt;ref&gt;{{cite journal |vauthors=Songserm T, Amonsin A, Jam-on R, Sae-Heng N, Pariyothorn N, Payungporn S, Theamboonlers A, Chutinimitkul S, Thanawongnuwech R, Poovorawan Y |title=Fatal avian influenza A H5N1 in a dog |journal=Emerging Infect. Dis. |volume=12 |issue=11 |pages=1744–7 |year=2006 |pmid=17283627 |doi=10.3201/eid1211.060542 |pmc=3372347}}&lt;/ref&gt;

The H3N2 virus made its first appearance in Canada at the start of 2018, following the importation of two unknowingly infected canines from South Korea. In 2006-2007 canine H3N2 first had reports in South Korea and was thought to be transferred to dogs from avian origins ([[avian influenza]] H3N2).&lt;ref&gt;{{Cite journal |last1=Voorhees |first1=Ian E. H. |last2=Glaser |first2=Amy L. |last3=Toohey-Kurth |first3=Kathy L. |last4=Newbury |first4=Sandra |last5=Dalziel |first5=Benjamin D. |last6=Dubovi |first6=Edward |last7=Poulsen |first7=Keith |last8=Leutenegger |first8=Christian |last9=Willgert |first9=Katriina J. E. |last10=Brisbane-Cohen |first10=Laura |last11=Richardson-Lopez |first11=Jill |last12=Holmes |first12=Edward C. |last13=Parrish |first13=Colin R. |title=Spread of Canine Influenza A(H3N2) Virus, United States - Volume 23, Number 12—December 2017 - Emerging Infectious Diseases journal - CDC |journal=Emerging Infectious Diseases |date=2017 |volume=23 |issue=12 |pages=1950–1957 |url=https://wwwnc.cdc.gov/eid/article/23/12/17-0246_article |language=en-us |doi=10.3201/eid2312.170246 |pmc=5708240 |pmid=28858604}}&lt;/ref&gt; It was not until 2015 that the canine H3N2 strain was discovered in the United States after there was an outbreak of dogs having respiratory infections in Chicago.&lt;ref name=&quot;:13&quot;&gt;{{Cite web |title=Canine influenza |url=https://www.avma.org/resources-tools/animal-health-and-welfare/canine-influenza |access-date=2023-09-29 |website=American Veterinary Medical Association |language=en}}&lt;/ref&gt; As canine H3N2 influenza began to spread through the United States, in 2016 cats in an Indiana began to show symptoms of the disease as well, it is believed they were infected by coming in to contact with sick dogs.&lt;ref name=&quot;:13&quot;/&gt;

Following this incidence, reports of the virus possibly spreading, with two other canines reporting alarming symptoms, were made public. By March 5, 25 cases of infection were reportedly spread, although the number is thought to be closer to approximately 100.&lt;ref&gt;{{Cite news|url=https://www.ctvnews.ca/barrie/article/canine-influenza-reported-in-several-dogs-in-orillia/|title=Canine influenza reported in several dogs in Orillia|last=Ward|first=Adam|date=2018-03-05|work=Barrie|access-date=2018-03-06|language=en-CA}}&lt;/ref&gt;

Influenza A viruses are [[Viral envelope|enveloped]], [[Sense (molecular biology)|negative sense]], single-stranded [[RNA virus]]es.&lt;ref&gt;ICTVdB Management (2006). 00.046.0.01. Influenzavirus A. In: ICTVdB - The Universal Virus Database, version 4. Büchen-Osmond, C. (Ed), Columbia University, New York, USA [https://web.archive.org/web/19990202065356/http://www.ncbi.nlm.nih.gov/ICTVdb/Ictv/index.htm]&lt;/ref&gt;  Genome analysis has shown that H3N8 was transferred from horses to dogs and then adapted to dogs through [[point mutation]]s in the [[gene]]s.&lt;ref name=&quot;Vetres&quot;&gt;{{cite journal |vauthors=Buonavoglia C, Martella V |title=Canine respiratory viruses |journal=Vet. Res. |volume=38 |issue=2 |pages=355–73 |year=2007 |pmid=17296161 |doi=10.1051/vetres:2006058|doi-access=free }}&lt;/ref&gt;  The [[incubation period]] is two to five days, and [[viral shedding]] may occur for seven to ten days following the onset of symptoms.&lt;ref name=&quot;UF&quot;&gt;{{cite web|title=Canine Influenza Virus (Canine Flu) |work=UF College of Veterinary Medicine Public Relations Office |date=2005-08-12 |url=http://www.vetmed.ufl.edu/pr/nw_story/CANINEFLUFACTSHEET.htm |access-date=2006-08-17 |archive-url=https://web.archive.org/web/20060717170950/http://www.vetmed.ufl.edu/pr/nw_story/CANINEFLUFACTSHEET.htm |archive-date=2006-07-17 |url-status=dead }}&lt;/ref&gt;  It does not induce a persistent [[Asymptomatic carrier|carrier]] state.{{citation needed|date=August 2022}}

In late 2022, together with [[Bordetella bronchiseptica]] and other respiratory pathogens, the H3N2 canine flu virus experienced a surge in canine infections. This was partially due to increased human travel and reopened offices following the relaxation of [[COVID-19 pandemic]] public health measures, leading to large numbers of dogs being placed together in kennels and doggy day care centers. Changing pet ownership behaviors also led to overcrowded animal shelters, which had been emptied at the height of the pandemic.&lt;ref name=&quot;2022 outbreak&quot;&gt;{{cite news |last1=Anthes |first1=Emily |title=Dog Flu Is Back, Too |url=https://www.nytimes.com/2022/12/02/health/dogs-canine-flu.html |access-date=17 December 2022 |work=New York Times |date=2 December 2022 |archive-url=https://web.archive.org/web/20221217151141/https://www.nytimes.com/2022/12/02/health/dogs-canine-flu.html |archive-date=17 December 2022}}&lt;/ref&gt;

== Transmissions ==
The infection of canine influenza can be transmitted from animal to animal and almost all dogs that come in contact with the virus will contract it. This makes canine influenza most common among dogs but can also be transmitted to cats in a shelter or a household.&lt;ref name=&quot;:03&quot;/&gt; Canine influenza is an [[airborne disease]], when a dog coughs or sneezes they secrete respiratory droplets that are then inhaled by other animals causing infection.&lt;ref name=&quot;:2&quot;&gt;{{Cite web |date=November 3, 2022 |first=Anna |last=Burke |title=What You Should Know About Dog Flu: Symptoms, Treatment, and Prevention |url=https://www.akc.org/expert-advice/health/the-dog-flu-symptoms-you-need-to-know/ |access-date=2023-09-29 |website=American Kennel Club |language=en}}&lt;/ref&gt; Kennels, dog parks, grooming parlors, and things alike are high risk areas for infections.&lt;ref name=&quot;:2&quot; /&gt;

==Symptoms==
About 80% of infected dogs with H3N8 show symptoms, usually mild (the other 20% have [[subclinical infection]]s), and the fatality rate for Greyhounds in early outbreaks was 5 to 8%,&lt;ref name=Carter/&gt; although the overall fatality rate in the general pet and shelter population is probably less than 1%.&lt;ref name=Vetmed&gt;{{cite journal | last = de Morais | first = Helio Autran | title = Canine influenza: Risks, management, and prevention | journal = Veterinary Medicine | volume = 101 | issue = 11 | pages = 714 | publisher = Advanstar Communications |date=November 2006 }}&lt;/ref&gt;  Most animals infected with canine influenza will show symptoms such as coughing, runny nose, fever, lethargy, eye discharge, and a reduced appetite lasting anywhere from 2–3 weeks.&lt;ref name=&quot;:03&quot;/&gt;

Symptoms of the mild form include a cough that lasts for 10 to 30 days and possibly a greenish nasal discharge.  Dogs with the more severe form may have a high fever and [[pneumonia]].&lt;ref name=&quot;AVMA&quot;&gt;{{cite web | title = Control of Canine Influenza in Dogs — Questions, Answers, and Interim Guidelines | publisher = [[American Veterinary Medical Association|AVMA]] | date = 2005-12-01 | url = http://www.avma.org/public_health/influenza/canine_guidelines.asp | access-date = 2006-08-17 | url-status = dead | archive-url = https://web.archive.org/web/20060813130552/http://www.avma.org/public_health/influenza/canine_guidelines.asp | archive-date = 2006-08-13 }}&lt;/ref&gt;  Pneumonia in these dogs is not caused by the influenza virus, but by secondary [[bacteria]]l infections.  The fatality rate of dogs that develop pneumonia secondary to canine influenza can reach 50% if not given proper treatment.&lt;ref name=&quot;Rosenthal2007&quot;&gt;{{cite journal | last = Rosenthal | first = Marie | title = Include new virus in the diagnosis of dogs with kennel cough | journal = Veterinary Forum | volume = 24 | issue = 2 | pages = 12–14 | publisher = Veterinary Learning Systems |date=February 2007 }}&lt;/ref&gt;  [[Necropsy|Necropsies]] in dogs that die from the disease have revealed severe [[hemorrhage|hemorrhagic]] pneumonia and evidence of [[vasculitis]].&lt;ref&gt;{{cite journal |vauthors=Yoon K, Cooper V, Schwartz K, Harmon K, Kim W, Janke B, Strohbehn J, Butts D, Troutman J |title=Influenza virus infection in racing greyhounds |journal=Emerging Infect. Dis. |volume=11 |issue=12 |pages=1974–6 |year=2005 |pmid=16485496 |doi=10.3201/eid1112.050810 |pmc=3367648}}&lt;/ref&gt;

==Diagnosis==
The presence of an upper respiratory tract infection in a dog that has been vaccinated for the other major causes of [[kennel cough]] increases suspicion of infection with canine influenza, especially in areas where the disease has been documented.  A [[blood plasma|serum]] sample from a dog suspected of having canine influenza can be submitted to a laboratory that performs [[Polymerase chain reaction|PCR]] tests for this virus.&lt;ref name=Vetmed/&gt;

==Vaccine==
In June 2009, the [[United States Department of Agriculture]] (USDA) [[Animal and Plant Health Inspection Service]] (APHIS) approved the first canine influenza vaccine.&lt;ref&gt;
{{cite press release|url=http://www.aphis.usda.gov/animal_health/vet_biologics/publications/notice_09_12.pdf |title=Aphis Issues Conditional License For Canine Influenza Virus Vaccine |date=23 June 2009 |publisher=[[Animal and Plant Health Inspection Service]] (APHIS) |access-date=2009-11-11 |url-status=dead |archive-url=https://web.archive.org/web/20160304192932/http://www.aphis.usda.gov/animal_health/vet_biologics/publications/notice_09_12.pdf |archive-date=March 4, 2016 }}&lt;/ref&gt;&lt;ref&gt;
{{cite web|url=http://www.intervetusa.com/news/2009-06-23.aspx |title=New Vaccine from Intervet/Schering-Plough Animal Health |date=23 June 2009 |publisher=Schering-Plough |access-date=2009-11-11 |url-status=dead |archive-url=https://web.archive.org/web/20100404033352/http://www.intervetusa.com/news/2009-06-23.aspx |archive-date=April 4, 2010 }}&lt;/ref&gt;&lt;ref&gt;
{{cite web
 |url=http://www.doginfluenza.com/pdfs/CIV_Vaccine_Backgrounder.pdf
 |title=Canine Influenza Virus (CIV) Backgrounder
 |year=2009
 |publisher=Schering-Plough
 |access-date=2009-11-11
 |url-status=dead
 |archive-url=https://web.archive.org/web/20110629144202/http://www.doginfluenza.com/pdfs/CIV_Vaccine_Backgrounder.pdf
 |archive-date=2011-06-29
}}&lt;/ref&gt;&lt;ref&gt;{{cite news
| last=McNeil Jr.
| first=Donald G.
| url=https://www.nytimes.com/2009/06/30/health/30flu.html
| title=New Flu Vaccine Approved -- for Dogs
| newspaper=The New York Times
| date=June 29, 2009
| access-date=2009-11-11
}}&lt;/ref&gt; This veterinarian provided vaccine help fight the infection and are preventative measures for dogs who are constantly facing exposure of the H3N8 and H3N2 strain.&lt;ref name=&quot;:13&quot;/&gt; This vaccine must be given twice initially with a two-week break, then annually thereafter.&lt;ref name=flu&gt;{{cite web|url=http://www.doginfluenza.com/Products/Overview.asp|series=Canine Influenza Vaccines|title=Dog Flu Vaccination Products|publisher=DogInfluenza.com|access-date=9 June 2016|archive-url=https://web.archive.org/web/20160630032115/http://www.doginfluenza.com/Products/Overview.asp|archive-date=30 June 2016|url-status=dead}}&lt;/ref&gt;

==H3N2 version==

A second form of canine influenza was first identified during 2006 in South Korea and southern China. The virus is an [[H3N2]] variant that adapted from its [[avian influenza]] origins.&lt;ref name=cornell1&gt;{{cite web|url=https://ahdc.vet.cornell.edu/docs/H3N2_FAQ_041415.pdf|publisher=[[Cornell University]]|title=FAQ about the H3N2 strain of canine influenza|access-date=2015-09-14}}&lt;/ref&gt; An outbreak in the US was first reported in the Chicago area during 2015.&lt;ref name=monitor&gt;{{cite web|url=https://ahdc.vet.cornell.edu/docs/CIV_Monitoring_2015-08-08r.pdf|title=Canine Influenza Virus Monitoring Effort|publisher=[[Cornell University]]|access-date=2015-09-14}}&lt;/ref&gt; Outbreaks were reported in several US states during the spring and summer of 2015&lt;ref name=monitor/&gt; and had been reported in 25 states by late 2015.&lt;ref name=nytnewflu/&gt;

As of April 2015, the question of whether vaccination against the earlier strain offered protection had not been resolved.&lt;ref name=cdc&gt;{{cite web|url=https://www.cdc.gov/flu/canineflu/keyfacts.htm|title=Key Facts about Canine Influenza (Dog Flu)|publisher=[[Centers for Disease Control]]|date=April 22, 2015|access-date=2015-09-14}}&lt;/ref&gt; The [[US Department of Agriculture]] granted  conditional approval for a canine H3N2-protective vaccine in December 2015.&lt;ref name=nytnewflu&gt;{{cite news|work=[[The New York Times]]|date=2015-12-15|author=Jan Hoffman|url=https://www.nytimes.com/2015/12/15/health/canine-flu-has-dog-owners-wondering-if-fido-needs-a-vaccine.html|title=Dog Owners Wondering if Fido Needs a Flu Shot|access-date=2015-12-22}}&lt;/ref&gt;&lt;ref name=flu/&gt;&lt;ref&gt;{{cite web|url=http://www.prnewswire.com/news-releases/merck-animal-health-pioneers-h3n2-canine-influenza-vaccine-300182707.html|title=Merck Animal Health Pioneers H3N2 Canine Influenza Vaccine|date=20 November 2015|publisher=Merck Animal Health|access-date=9 June 2016}}&lt;/ref&gt;&lt;ref&gt;{{cite web|url=https://www.zoetisus.com/products/dogs/CanineInfluenzaVaccineH3N2/|title=Canine Influenza Vaccine, H3N2, Killed Virus|publisher=Zoetis|access-date=9 June 2016}}&lt;/ref&gt;

In March 2016, researchers reported that this strain had infected cats and suggested that it may be transmitted between them.&lt;ref&gt;{{cite web|url=https://www.avma.org/KB/Resources/Reference/Pages/Canine-Influenza-Backgrounder.aspx|publisher=[[American Veterinary Medical Association]]|title=Canine Influenza|access-date=2016-06-11|archive-url=https://web.archive.org/web/20181214164151/https://www.avma.org/KB/Resources/Reference/Pages/Canine-Influenza-Backgrounder.aspx|archive-date=2018-12-14|url-status=dead}}&lt;/ref&gt;

== Human risk ==
The H3N2 virus as a stand-alone virus is deemed harmless to humans. According to the Windsor-Essex County Health Unit, it is only when the H3N2 virus strain combines with a human strain of flu, &quot;those strains could combine to create a new virus.&quot; The possibility of this is unlikely; however, if an infected dog contracts a human flu, there stands a slight chance.&lt;ref&gt;{{Cite news|url=http://www.cbc.ca/news/canada/windsor/confirmed-case-canine-influenza-essex-1.4477588|title=First 2 cases of canine influenza confirmed in Canada|work=CBC News|access-date=2018-01-09|language=en}}&lt;/ref&gt;

==See also==
{{Portal|Dogs}}
* [[Avian influenza]]
* [[Equine influenza]]
* [[Influenza|Human flu]]
* [[Swine influenza]]
* [[Cat flu]]

==References==
{{Reflist|refs=
&lt;ref name=&quot;CDC&quot;&gt;{{cite web
 |title=Media Briefing on Canine Influenza
 |publisher=CDC
 |url=https://www.cdc.gov/od/oc/media/transcripts/t050926.htm
 |access-date=2007-04-21
 |archive-url=https://web.archive.org/web/20070410004420/http://www.cdc.gov/od/oc/media/transcripts/t050926.htm
 |date=September 26, 2005
 |archive-date=2007-04-10
 |url-status=dead
}}
&lt;/ref&gt;&lt;ref name=&quot;VF&quot;&gt;{{cite journal
  | last=Rosenthal | first=Marie
  | title=CIV may have started circulating earlier than originally thought
  | journal=Veterinary Forum | volume=24 | issue=7 | pages=12
  | publisher=Veterinary Learning Systems |date=July 2007 }}
&lt;/ref&gt;&lt;ref name=&quot;Carter&quot;&gt;{{cite web |author1=Carter, G.R. |author2=Flores, E.F. |author3=Wise, D.J. |year=2006 |title=Orthomyxoviridae |work=A Concise Review of Veterinary Virology |url=http://www.ivis.org/advances/carter/Part2Chap20/chapter.asp?LA=1#Canine |access-date=2006-08-17 }}{{Dead link|date=October 2023 |bot=InternetArchiveBot |fix-attempted=yes }}&lt;/ref&gt;
}}

==Further reading==
* [https://www.nytimes.com/2005/09/22/national/22canine.html?ex=1285041600&amp;en=738389c5f9f98dfd&amp;ei=5088&amp;partner=rssnyt&amp;emc=rss A New Deadly, Contagious Dog Flu Virus Is Detected in 7 States] The New York Times
* [https://ahdc.vet.cornell.edu/news/civchicago.cfm States that have identified dogs with CIV]
* [http://www.veterinarypartner.com/Content.plx?P=A&amp;S=0&amp;C=0&amp;A=2165 ''Canine Influenza'' from The Pet Health Library]
* [http://www.veterinarypartner.com/Content.plx?P=A&amp;S=0&amp;C=0&amp;A=2146 ''Canine Influenza'' from Veterinary Partner]
* [http://www.cfsph.iastate.edu/Factsheets/pdfs/canine_influenza.pdf Canine Influenza Fact Sheet] Center for Food Security and Public Health (CFSPH), [[Iowa State University College of Veterinary Medicine]]
* [https://web.archive.org/web/20181214164151/https://www.avma.org/KB/Resources/Reference/Pages/Canine-Influenza-Backgrounder.aspx AVMA: canine influenza]

{{influenza}}

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[[Category:Dog diseases|Influenza]]
[[Category:Influenza]]
[[Category:Animal viral diseases]]
[[Category:Vaccine-preventable diseases]]