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Influenza A virus

Influenza A virus
Structure of influenza A virus
Transmission electron micrograph of influenza A viruses (light objects on a dark background).
TEM micrograph of influenza A viruses
Virus classification Edit this classification
(unranked): Virus
Realm: Riboviria
Kingdom: Orthornavirae
Phylum: Negarnaviricota
Class: Insthoviricetes
Order: Articulavirales
Family: Orthomyxoviridae
Genus: Alphainfluenzavirus
Species:
Influenza A virus

Influenza A virus (IAV) is the only species of the genus Alphainfluenzavirus of the virus family Orthomyxoviridae.[1] It is a pathogen with strains that infect birds and some mammals, as well as causing seasonal flu in humans.[2] Mammals in which different strains of IAV circulate with sustained transmission are bats, pigs, horses and dogs; other mammals can occasionally become infected.[3][4]

IAV is an enveloped negative-sense RNA virus, with a segmented genome.[4] Through a combination of mutation and genetic reassortment the virus can evolve to acquire new characteristics, enabling it to evade host immunity and occasionally to jump from one species of host to another.[5][6]

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.[7] Almost all possible combinations of H (1 thru 16) and N (1 thru 11) have been isolated from wild birds.[8] Further variations exist within the subtypes and can lead to very significant differences in the virus's ability to infect and cause disease, as well as to the severity of symptoms.[9][10]

Symptoms of human seasonal flu usually include fever, cough, sore throat, muscle aches, conjunctivitis and, in severe cases, breathing problems and pneumonia that may be fatal.[11][2] Humans can rarely become infected with strains of avian or swine influenza, usually as a result of close contact with infected animals; symptoms range from mild to severe including death.[12][13] Bird-adapted strains of the virus can be asymptomatic in some aquatic birds but lethal if they spread to other species, such as chickens.[14]

IAV disease in poultry can be can be prevented by vaccination, however biosecurity control measures are preferred.[15][16] In humans, seasonal influenza can be treated in its early stages with antiviral medicines.[17] A global network, the Global Influenza Surveillance and Response System (GISRS) monitors the spread of influenza with the aim to inform development of both seasonal and pandemic vaccines.[18] Several millions of specimens are tested by the GISRS network annually through a network of laboratories in 127 countries. As well as human viruses, GISRS monitors avian, swine, and other potentially zoonotic influenza viruses. IAV vaccines need to be reformulated regularly in order to keep up with changes in the virus.[19]

  1. ^ "Taxonomy". International Committee on Taxonomy of Viruses (ICTV). Archived from the original on 20 March 2020. Retrieved 19 July 2018.
  2. ^ a b Cite error: The named reference :7 was invoked but never defined (see the help page).
  3. ^ Runstadler JA, Puryear W (2020). "A Brief Introduction to Influenza A Virus in Marine Mammals". Animal Influenza Virus. Methods in Molecular Biology (Clifton, N.J.). Vol. 2123. pp. 429–450. doi:10.1007/978-1-0716-0346-8_33. ISBN 978-1-0716-0345-1. ISSN 1940-6029. PMID 32170708.
  4. ^ a b "Influenza A Subtypes and the Species Affected | Seasonal Influenza (Flu) | CDC". Centers for Disease Control and Prevention. 13 May 2024. Retrieved 17 June 2024.
  5. ^ 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.
  6. ^ 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.
  7. ^ CDC (1 February 2024). "Influenza Type A Viruses". Centers for Disease Control and Prevention. Retrieved 3 May 2024.
  8. ^ "FluGlobalNet - Avian Influenza". science.vla.gov.uk. Retrieved 5 June 2024.
  9. ^ CDC (30 March 2023). "Types of Influenza Viruses". Centers for Disease Control and Prevention. Retrieved 17 June 2024.
  10. ^ CDC (11 June 2024). "Avian Influenza Type A Viruses". Avian Influenza (Bird Flu). Retrieved 17 June 2024.
  11. ^ "Flu". National Health Service. 23 October 2017. Retrieved 17 June 2024.
  12. ^ "Avian influenza: guidance, data and analysis". GOV.UK. 18 November 2021. Retrieved 9 May 2024.
  13. ^ "Swine influenza in humans". European Centre for Disease Prevention and Control (ECDC). 20 September 2017. Retrieved 17 June 2024.
  14. ^ 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.
  15. ^ "Avian influenza (bird flu)". European Medicines Agency. 12 June 2024. Retrieved 18 June 2024.
  16. ^ "Avian influenza (bird flu) vaccination". UK Government - Department for Environment Food & Rural Affairs. 5 June 2023. Retrieved 18 June 2024.
  17. ^ CDC (20 March 2024). "What You Should Know about Flu Antiviral Drugs". Centers for Disease Control and Prevention. Retrieved 18 June 2024.
  18. ^ Lee K, Fang J (2013). Historical Dictionary of the World Health Organization. Rowman & Littlefield. ISBN 9780810878587.
  19. ^ "70 years of GISRS – the Global Influenza Surveillance & Response System". World Health Organization. 19 September 2022. Retrieved 13 June 2024.

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