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__NOTOC__
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{{Avian influenza}}
{{Avian influenza}}'''For more information about seasonal human influenza virus that is not associated with animal exposure, see [[Influenza]]'''<br><br>
{{CMG}}
{{CMG}}; {{AE}} {{YD}}
==Overview==
To date, only influenza type A has been associated with avian influenza. Neither [[influenza B]] nor [[influenza C]] is associated with avian influenza. Classification of avian influenza may be based on either the [[pathogenicity]] of the virus (low pathogenicity vs. high pathogenicity) or the viral genetic subtypes (H5 vs. H7 vs. H9).


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==Classification==
==Classification==
===H5N1 Subtype===
Classification of avian influenza may be based on either the pathogenicity of the virus or the viral genetic subtypes. To date, only influenza type A has been associated with avian influenza.
{{H5N1}}
{{details more|H5N1|Transmission and infection of H5N1}}
The highly [[pathogenic]] [[Influenza A virus]] subtype [[H5N1]] [[virus]] is an emerging avian [[influenza virus]] that has been causing global concern as a potential [[pandemic]] threat. It is often referred to simply as "bird flu" or "avian [[influenza]]" even though it is only one subtype of avian [[influenza]] causing [[virus]].  


[[H5N1]] has killed millions of poultry in a growing number of countries throughout Asia, Europe and Africa. Health experts are concerned that the co-existence of human flu [[virus]]es and avian flu [[virus]]es (especially [[H5N1]]) will provide an opportunity for [[genetic]] material to be exchanged between [[species]]-specific [[virus]]es, possibly creating a new [[virulent]] [[influenza]] strain that is easily [[transmission|transmissible]] and lethal to humans.<ref name=FSRIO>Food Safety Research Information Office. [http://fsrio.nal.usda.gov/document_fsheet.php?product_id=207 "A Focus on Avian Influenza"]. Created May 2006, Updated November 2007.</ref>
===Classification Based on Pathogenecity of the Virus===
Avian influenza may be classified based on the pathogenicity of the virus:
*Low pathogenic avian influenza (LPAI)
::Mild/no [[Avian influenza history and symptoms|clinical manifestation]]s among humans
::May convert to highly pathogenic avian influenza


Since the first [[H5N1]] [[outbreak]] occurred in 1997, there has been an increasing number of HPAI [[H5N1]] bird-to-human [[transmission]]s leading to clinically severe and fatal human [[infection]]s. However, because there is a significant [[species]] barrier that exists between birds and humans, the [[virus]] does not easily cross over to humans, though some cases of [[infection]] are being researched to discern whether human to human [[transmission]] is occurring. More research is necessary to understand the [[pathogenesis]] and [[epidemiology]] of the [[H5N1]] [[virus]] in humans. Exposure routes and other disease [[transmission]] characteristics such as [[genetic]] and [[immunological]] factors, that may increase the likelihood of [[infection]], are not clearly understood.
*Highly pathogenic avian influenza (HPAI)
::Moderate/severe [[Avian influenza history and symptoms|clinical manifestation]]s among humans
::Viral subtypes H5 and H7 are associated with HPAI


Although millions of birds have become [[infect]]ed with the [[virus]] since its discovery, 206 humans have died from the [[H5N1]] in twelve countries according to [[WHO]] data as of November 2007.
===Classification Based on Viral Genetic Subtypes===
*To date, only influenza type A has been associated with avian influenza. Neither influenza B nor influenza C is associated with avian influenza.
*Although avian influenza has many subtypes of [[haemagglutinin]] (HA) and [[neuraminidase]] (NA), only 3 subtypes have been associated with human infections.
*The table below lists the subtypes of influenza A that have been associated with avian influenza in humans:<ref name="pmid23577628">{{cite journal |vauthors=Gao R, Cao B, Hu Y, Feng Z, Wang D, Hu W, Chen J, Jie Z, Qiu H, Xu K, Xu X, Lu H, Zhu W, Gao Z, Xiang N, Shen Y, He Z, Gu Y, Zhang Z, Yang Y, Zhao X, Zhou L, Li X, Zou S, Zhang Y, Li X, Yang L, Guo J, Dong J, Li Q, Dong L, Zhu Y, Bai T, Wang S, Hao P, Yang W, Zhang Y, Han J, Yu H, Li D, Gao GF, Wu G, Wang Y, Yuan Z, Shu Y |title=Human infection with a novel avian-origin influenza A (H7N9) virus |journal=N. Engl. J. Med. |volume=368 |issue=20 |pages=1888–97 |year=2013 |pmid=23577628 |doi=10.1056/NEJMoa1304459 |url=}}</ref><ref name="pmid23643111">{{cite journal |vauthors=Liu D, Shi W, Shi Y, Wang D, Xiao H, Li W, Bi Y, Wu Y, Li X, Yan J, Liu W, Zhao G, Yang W, Wang Y, Ma J, Shu Y, Lei F, Gao GF |title=Origin and diversity of novel avian influenza A H7N9 viruses causing human infection: phylogenetic, structural, and coalescent analyses |journal=Lancet |volume=381 |issue=9881 |pages=1926–32 |year=2013 |pmid=23643111 |doi=10.1016/S0140-6736(13)60938-1 |url=}}</ref><ref name="pmid23650290">{{cite journal |vauthors=Xiong C, Zhang Z, Jiang Q, Chen Y |title=Evolutionary characteristics of A/Hangzhou/1/2013 and source of avian influenza virus H7N9 subtype in China |journal=Clin. Infect. Dis. |volume=57 |issue=4 |pages=622–4 |year=2013 |pmid=23650290 |doi=10.1093/cid/cit294 |url=}}</ref>


The Avian Flu claimed at least 200 humans in Romania, Greece, Turkey and Russia. [[Epidemiologist]]s are afraid that the next time such a [[virus]] [[mutation|mutates]], it could pass from human to human. If this form of transmission occurs, another big pandemic could result. However, disease-control centers around the world are making avian flu their top priority.
{| style="border: 0px; font-size: 90%; margin: 3px;" align=center
|+
! style="background: #4479BA; width: 120px;" | {{fontcolor|#FFF|Influenza Subtype}}
! style="background: #4479BA; width: 120px;" | {{fontcolor|#FFF|Number of Subtypes}}
! style="background: #4479BA; width: 200px;" | {{fontcolor|#FFF|Pathogenicity}}
! style="background: #4479BA; width: 150px;" | {{fontcolor|#FFF|Clinical Manifestations}}
|-
| style="padding: 5px 5px; background: #DCDCDC;" | '''[[Influenza A H5]]'''
| style="padding: 5px 5px; background: #F5F5F5;" | At least 9
| style="padding: 5px 5px; background: #F5F5F5;" | May be either HPAI or LPAI


'''Bird flu''' may refer to:
| style="padding: 5px 5px; background: #F5F5F5;" | May cause either mild or severe/fatal clinical manifestations
* [[Avian influenza]] - another name for bird flu or avian influenza
|-
* [[H5N1]] - the current type of bird flu virus that is the worst pandemic threat
| style="padding: 5px 5px; background: #DCDCDC;" | '''[[Influenza A H7]]'''
* [[Influenzavirus A|Influenza A virus]] - the species of virus that causes all bird flu.
| style="padding: 5px 5px; background: #F5F5F5;" | At least 9
 
| style="padding: 5px 5px; background: #F5F5F5;" | May be either HPAI or LPAI
 
| style="padding: 5px 5px; background: #F5F5F5;" | May cause either mild or severe/fatal clinical manifestations
 
|-
| style="padding: 5px 5px; background: #DCDCDC;" | '''[[Influenza A H9]]'''
| style="padding: 5px 5px; background: #F5F5F5;" | At least 9
| style="padding: 5px 5px; background: #F5F5F5;" | Only reported as LPAI
 
| style="padding: 5px 5px; background: #F5F5F5;" | Mild clinical manifestations in humans
|-
|}


==References==
==References==


{{Reflist|2}}
{{Reflist|2}}
[[Category:Needs content]]
[[Category:Pandemics]]
[[Category:Occupational safety and health]]
[[Category:Influenza]]
[[Category:Bird diseases]]
[[Category:Infectious diseases]]
[[Category:Avian influenza]]
[[Category:Medicine]]
[[Category:Infectious disease]]
[[Category:Virology]]
[[Category:Animal virology]]
[[Category:Microbiology]]
[[Category:Microbiology]]
[[Category:Poultry diseases]]
[[Category:Emergency medicine]]
[[Category:Pulmonology]]
[[Category:Pulmonology]]
[[Category:Disease]]
[[Category:Occupational safety and health]]


{{WH}}
{{WH}}
{{WS}}
{{WS}}

Latest revision as of 15:56, 17 February 2017

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For more information about seasonal human influenza virus that is not associated with animal exposure, see Influenza

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Yazan Daaboul, M.D.

Overview

To date, only influenza type A has been associated with avian influenza. Neither influenza B nor influenza C is associated with avian influenza. Classification of avian influenza may be based on either the pathogenicity of the virus (low pathogenicity vs. high pathogenicity) or the viral genetic subtypes (H5 vs. H7 vs. H9).

Classification

Classification of avian influenza may be based on either the pathogenicity of the virus or the viral genetic subtypes. To date, only influenza type A has been associated with avian influenza.

Classification Based on Pathogenecity of the Virus

Avian influenza may be classified based on the pathogenicity of the virus:

  • Low pathogenic avian influenza (LPAI)
Mild/no clinical manifestations among humans
May convert to highly pathogenic avian influenza
  • Highly pathogenic avian influenza (HPAI)
Moderate/severe clinical manifestations among humans
Viral subtypes H5 and H7 are associated with HPAI

Classification Based on Viral Genetic Subtypes

  • To date, only influenza type A has been associated with avian influenza. Neither influenza B nor influenza C is associated with avian influenza.
  • Although avian influenza has many subtypes of haemagglutinin (HA) and neuraminidase (NA), only 3 subtypes have been associated with human infections.
  • The table below lists the subtypes of influenza A that have been associated with avian influenza in humans:[1][2][3]
Influenza Subtype Number of Subtypes Pathogenicity Clinical Manifestations
Influenza A H5 At least 9 May be either HPAI or LPAI May cause either mild or severe/fatal clinical manifestations
Influenza A H7 At least 9 May be either HPAI or LPAI May cause either mild or severe/fatal clinical manifestations
Influenza A H9 At least 9 Only reported as LPAI Mild clinical manifestations in humans

References

  1. ↑ Gao R, Cao B, Hu Y, Feng Z, Wang D, Hu W, Chen J, Jie Z, Qiu H, Xu K, Xu X, Lu H, Zhu W, Gao Z, Xiang N, Shen Y, He Z, Gu Y, Zhang Z, Yang Y, Zhao X, Zhou L, Li X, Zou S, Zhang Y, Li X, Yang L, Guo J, Dong J, Li Q, Dong L, Zhu Y, Bai T, Wang S, Hao P, Yang W, Zhang Y, Han J, Yu H, Li D, Gao GF, Wu G, Wang Y, Yuan Z, Shu Y (2013). "Human infection with a novel avian-origin influenza A (H7N9) virus". N. Engl. J. Med. 368 (20): 1888–97. doi:10.1056/NEJMoa1304459. PMID 23577628.
  2. ↑ Liu D, Shi W, Shi Y, Wang D, Xiao H, Li W, Bi Y, Wu Y, Li X, Yan J, Liu W, Zhao G, Yang W, Wang Y, Ma J, Shu Y, Lei F, Gao GF (2013). "Origin and diversity of novel avian influenza A H7N9 viruses causing human infection: phylogenetic, structural, and coalescent analyses". Lancet. 381 (9881): 1926–32. doi:10.1016/S0140-6736(13)60938-1. PMID 23643111.
  3. ↑ Xiong C, Zhang Z, Jiang Q, Chen Y (2013). "Evolutionary characteristics of A/Hangzhou/1/2013 and source of avian influenza virus H7N9 subtype in China". Clin. Infect. Dis. 57 (4): 622–4. doi:10.1093/cid/cit294. PMID 23650290.

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