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DRAFT MATERIAL

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Compiled version of influenza lead

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  • H?N? is a subtype of the influenza A virus, which causes avian flu in birds. It is enzootic (maintained in the population) in many bird populations, especially aquatic birds which may display no symptoms and can potentially spread the virus over long distances in their annual migration..[1] Infected birds shed the virus in their saliva and feces. The H?N? virus can also infect mammals (including humans) that have been exposed to infected birds.[2]
  • Each year, three influenza strains are chosen for inclusion in the forthcoming year's seasonal flu vaccination by the Global Influenza Surveillance and Response System of the World Health Organization (WHO). Since 1999, every annual formulation has included one strain of A/H?N? as well as two other influenza strains - together representing strains thought most likely to cause significant human suffering in the coming season.[3][4][5]

Raw material

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  • Influenza A virus subtype H7N9 (A/H7N9) is a subtype of the influenza A virus, which causes influenza (flu), predominantly in birds. It is enzootic (maintained in the population) in many bird populations.[6] A/H7N9 virus can also infect humans that have been exposed to infected birds; in these cases, symptoms are frequently severe or fatal.[7] A/H7N9 virus is shed in the saliva, mucous, and feces of infected birds.[8] The virus can spread rapidly through poultry flocks and among wild birds.[8] Symptoms of A/H7N9 influenza vary according to both the strain of virus underlying the infection and on the species of bird or mammal affected.[9][10] Classification as either Low Pathogenic Avian Influenza (LPAI) or High Pathogenic Avian Influenza (HPAI) is based on the severity of symptoms in domestic chickens and does not predict the severity of symptoms in humans.[11] Chickens infected with LPAI A/H7N9 virus display mild symptoms or are asymptomatic, whereas HPAI A/H7N9 causes serious breathing difficulties, a significant drop in egg production, and sudden death.[12] In humans, A/H7N9 influenza (whether LPAI or HPAI) is rare; it can usually be traced to close contact with infected poultry or contaminated material such as feces.[13] Symptoms of infection vary from mild to severe, including fever, diarrhoea, and cough.[14] The H7N9 virus is considered to be enzootic (continually present) in wild aquatic birds, which may carry the virus over large distances during their migration.[15]
  • Influenza A virus subtype H1N1 (A/H1N1) is a subtype of influenza A virus (IAV). Some human-adapted strains of H1N1 are endemic in humans and are one cause of seasonal influenza (flu).[16] Other strains of H1N1 are endemic in pigs (swine influenza) and in birds (avian influenza).[17] Subtypes of IAV are defined by the combination of the antigenic H and N proteins in the viral envelope; for example, "H1N1" designates an IAV subtype that has a type-1 hemagglutinin (H) protein and a type-1 neuraminidase (N) protein.[18] All subtypes of IAV share a negative-sense, segmented RNA genome.[16] Under rare circumstances, one strain of the virus can acquire genetic material through genetic reassortment from a different strain and thus evolve to acquire new characteristics, enabling it to evade host immunity and occasionally to jump from one species of host to another.[19][20] Major outbreaks of H1N1 strains in humans include the 1918 Spanish flu pandemic, the 1977 Russian flu pandemic and the 2009 swine flu pandemic, all of which were caused by strains of A(H1N1) virus which are believed to have undergone genetic reassortment.[21]
  • Influenza A virus subtype H3N2 (A/H3N2) is a subtype of viruses that causes influenza (flu). H3N2 viruses can infect birds and mammals. In birds, humans, and pigs, the virus has mutated into many strains. In years in which H3N2 is the predominant strain, there are more hospitalizations.[22]
  • H3N2 is a subtype of the viral genus Influenzavirus A, which is an important cause of human influenza. Its name derives from the forms of the two kinds of proteins on the surface of its coat, hemagglutinin (H) and neuraminidase (N). By reassortment, H3N2 exchanges genes for internal proteins with other influenza subtypes.[23]

Subtypes

This section is an excerpt from Avian influenza § Subtypes.[edit]

Subtypes of influenza A are defined by the combination of H and N proteins in the viral envelope; for example, "H5N1" designates an influenza A subtype that has a type-5 hemagglutinin (H) protein and a type-1 neuraminidase (N) protein.[24] The subtyping scheme only takes into account the two envelope proteins, not the other proteins coded by the virus' RNA. Almost all possible combinations of H (1 thru 16) and N (1 thru 11) have been isolated from wild birds.[25] Further variations exist within the subtypes and can lead to very significant differences in the virus's ability to infect and cause disease.[26]

Keep for future reference

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Hidden text & footnote

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... and a footnote.[a]

H5N1 deaths (transcluded from Influenza A virus subtype H5N1

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Between 2003 and July 2024, the World Health Organization has recorded 904 cases of confirmed H5N1 influenza, leading to 463 deaths.[27] The true fatality rate may be lower because some cases with mild symptoms may not have been identified as H5N1.[28]


References and notes

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  1. ^ Explanatory footnote here
  1. ^ "Influenza (Avian and other zoonotic)". who.int. World Health Organization. 3 October 2023. Retrieved 2024-05-06.
  2. ^ Bourk, India (26 April 2024). "'Unprecedented': How bird flu became an animal pandemic". bbc.com. BBC. Retrieved 2024-05-08.
  3. ^ "Seasonal Flu Vaccines | CDC". Centers for Disease Control and Prevention. 2024-03-12. Retrieved 2024-08-19.
  4. ^ "Global Influenza Surveillance and Response System (GISRS)". World Health Organization. Archived from the original on October 3, 2011. Retrieved October 22, 2019.
  5. ^ Anker M, Schaaf D, World Health Organization (2000). WHO report on global surveillance of epidemic-prone infectious diseases (PDF) (Report). World Health Organization (WHO). hdl:10665/66485. WHO/CDS/CSR/ISR/2000.1. Archived (PDF) from the original on 31 October 2022.
  6. ^ "Influenza (Avian and other zoonotic)". who.int. World Health Organization. 3 October 2023. Retrieved 2024-05-06.
  7. ^ "Avian Influenza A(H7N9) virus". Food and Agricultural Organization of the United Nations. 1 June 2022. Retrieved 2024-07-15.
  8. ^ a b "Prevention and Antiviral Treatment of Bird Flu Viruses in People | Avian Influenza (Flu)". cdc.gov. US: Centers for Disease Control. 2024-04-19. Retrieved 2024-05-08.
  9. ^ "Bird flu (avian influenza)". betterhealth.vic.gov.au. Victoria, Australia: Department of Health & Human Services. Retrieved 2024-05-09.
  10. ^ "Avian influenza: guidance, data and analysis". gov.uk. 2021-11-18. Retrieved 2024-05-09.
  11. ^ "Avian Influenza in Birds". cdc.gov. US: Centers for Disease Control and Prevention. 2022-06-14. Retrieved 2024-05-06.
  12. ^ "Bird flu (avian influenza): how to spot and report it in poultry or other captive birds". gov.uk. UK: Department for Environment, Food & Rural Affairs and Animal and Plant Health Agency. 2022-12-13. Retrieved 2024-05-06.
  13. ^ "Frequently Asked Questions on human infection with influenza A(H7N9) virus, China". World Health Organization. 5 April 2013. Archived from the original on February 13, 2014. Retrieved 9 April 2013.
  14. ^ "Avian influenza: guidance, data and analysis". gov.uk. 2021-11-18. Retrieved 2024-05-09.
  15. ^ Joseph U, Su YC, Vijaykrishna D, Smith GJ (January 2017). "The ecology and adaptive evolution of influenza A interspecies transmission". Influenza and Other Respiratory Viruses. 11 (1): 74–84. doi:10.1111/irv.12412. PMC 5155642. PMID 27426214.
  16. ^ a b "Influenza A Subtypes and the Species Affected | Seasonal Influenza (Flu) | CDC". Centers for Disease Control and Prevention. 2024-05-13. Retrieved 2024-06-17.
  17. ^ Jilani TN, Jamil RT, Siddiqui AH (November 30, 2020). "H1N1 Influenza". H1N1 Influenza in StatPearls. StatPearls. PMID 30020613. Archived from the original on 12 March 2020. Retrieved 25 August 2020.
  18. ^ CDC (2024-02-01). "Influenza Type A Viruses". Centers for Disease Control and Prevention. Retrieved 2024-05-03.
  19. ^ Shao W, Li X, Goraya MU, Wang S, Chen JL (August 2017). "Evolution of Influenza A Virus by Mutation and Re-Assortment". International Journal of Molecular Sciences. 18 (8): 1650. doi:10.3390/ijms18081650. PMC 5578040. PMID 28783091.
  20. ^ Eisfeld AJ, Neumann G, Kawaoka Y (January 2015). "At the centre: influenza A virus ribonucleoproteins". Nature Reviews. Microbiology. 13 (1): 28–41. doi:10.1038/nrmicro3367. PMC 5619696. PMID 25417656.
  21. ^ Clancy, Susan (2008). "Genetics of the Influenza Virus | Learn Science at Scitable". www.nature.com. Nature Education 1(1):83. Retrieved 2024-08-17.
  22. ^ "Pinkbook | Influenza | Epidemiology of Vaccine Preventable Diseases | CDC". CDC. 2019-03-29. Retrieved 6 June 2019. Greater number of hospitalizations during years that A(H3N2) is predominant
  23. ^ Marozin, S.; Gregory, V.; Cameron, K.; Bennett, M.; Valette, M.; Aymard, M.; Foni, E.; Barigazzi, G.; Lin, Y.; Hay, A.YR 2002 (2002). "Antigenic and genetic diversity among swine influenza A H1N1 and H1N2 viruses in Europe". Journal of General Virology. 83 (4): 735–745. doi:10.1099/0022-1317-83-4-735. ISSN 1465-2099. PMID 11907321.{{cite journal}}: CS1 maint: numeric names: authors list (link)
  24. ^ "Influenza Type A Viruses". U.S. Centers for Disease Control and Prevention (CDC). 2024-02-01. Retrieved 2024-05-03.
  25. ^ "FluGlobalNet - Avian Influenza". science.vla.gov.uk. Retrieved 2024-06-05.
  26. ^ Eisfeld AJ, Neumann G, Kawaoka Y (January 2015). "At the centre: influenza A virus ribonucleoproteins". Nature Reviews. Microbiology. 13 (1): 28–41. doi:10.1038/nrmicro3367. PMC 5619696. PMID 25417656.
  27. ^ "Avian influenza A(H5N1) virus". www.who.int. Retrieved 2024-05-28.
  28. ^ Li FC, Choi BC, Sly T, Pak AW (June 2008). "Finding the real case-fatality rate of H5N1 avian influenza". J Epidemiol Community Health. 62 (6): 555–9. doi:10.1136/jech.2007.064030. PMID 18477756. S2CID 34200426.
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