Avian influenza classification
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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
- ↑ 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.
- ↑ 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.
- ↑ 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.