Video:Influenza A virus

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Definition

Influenza A virus causes influenza in birds and some mammals, and is the only species of the genus Alphainfluenzavirus of the virus family Orthomyxoviridae.[1]Occasionally, viruses are transmitted from wild aquatic birds to domestic poultry, and this may cause an outbreak or give rise to human influenza pandemics.[2][3]The influenza A virus subtypes that have been confirmed in humans, are H1N1 which caused the Spanish flu in 1918 and the 2009 swine flu pandemic.[4]

Structure

The virus particle is 80 to 120 nanometers in diameter such that the smallest virions adopt an elliptical shape.[5][6] The length of each particle varies considerably, owing to the fact that influenza is pleomorphic, and can be in excess of many tens of micrometers, producing filamentous virions.[7]

Genome

The genome is made up of the following segments-PB2, PB1, PA, HA, NP, NA ,M and finally segment 8 encodes two distinct non-structural proteins (NS1 and NEP) by using different reading frames from the same RNA segment.[8][9]

Transmission

Typically influenza is transmitted from infected birds through their droppings. Out of a host, flu viruses can remain infectious for about one week at human body temperature, over 30 days at 0 degrees celsius, and indefinitely at very low temperatures.[10][11][12]

Replication

The viruses bind to a cell through interactions between its hemagglutinin glycoprotein and sialic acid sugars on the surfaces of epithelial cells in the lung and throat.[13] The cell imports the virus by endocytosis. In the acidic endosome, part of the hemagglutinin protein fuses the viral envelope with the vacuole's membrane, releasing the viral RNA molecules, accessory proteins and RNA-dependent RNA polymerase into the cytoplasm .[14]

Multiplicity reactivation

Influenza virus is able to undergo multiplicity reactivation after inactivation by UV radiation, or by ionizing radiation. When two or more damaged viruses infect the same cell, viable progeny viruses can be produced provided each of the eight genomic segments is present in at least one undamaged copy.[15][16][17][18]

Subtypes

Some of the influenza A virus subtypes that have been confirmed in humans are the following: H1N1 (Spanish flu) 1917[19], H1N1 (Swine flu) 2009[20], H2N2 (Asian flu) 1957[21], H3N2 (Hong Kong flu) 1968[22], H5N1 2006[23], H7N9[24], H7N7[25][26] and H1N2[27].

H1N1

H1N1 was responsible for the 2009 pandemic in both human and pig populations. A variant of H1N1 was responsible for the Spanish flu pandemic, that killed some 50 million to 100 million people worldwide over about a year in 1918 and 1919.[28]

H3N2

H3N2 is endemic in both human and pig populations. It evolved from H2N2 by antigenic shift and caused the Hong Kong flu pandemic of 1968, and 1969, that killed up to three quarters of a million people.[29] A severe form of the H3N2 virus killed several children in the United States in late 2003.[30]

Vaccine

Globally the toll of influenza virus is estimated at two hundred ninety thousand to six hundred forty five thousand deaths annually.[31]The annually updated, trivalent influenza vaccine consists of hemagglutinin (HA) surface glycoprotein components from influenza H3N2, H1N1, and B influenza viruses.[32]

Evolution

All influenza A pandemics since the Spanish flu pandemic, and indeed almost all cases of influenza A worldwide excepting human infections from avian viruses such as H5N1 and H7N7, have been caused by descendants of the 1918 virus, including drifted H1N1 viruses and reassorted H2N2 and H3N2 viruses.[33]

References

  1. ↑ "Taxonomy". International Committee on Taxonomy of Viruses (ICTV). Retrieved 2018-07-19.
  2. ↑ Klenk H, Matrosovich M, Stech J (2008). "Avian Influenza: Molecular Mechanisms of Pathogenesis and Host Range". In Mettenleiter TC, Sobrino F (eds.). Animal Viruses: Molecular Biology. Caister Academic Press. ISBN 978-1-904455-22-6.
  3. ↑ Kawaoka Y, ed. (2006). Influenza Virology: Current Topics. Caister Academic Press. ISBN 978-1-904455-06-6.
  4. ↑ Jilani, Talha N.; Jamil, Radia T.; Siddiqui, Abdul H. (2022). "H1N1 Influenza". StatPearls. StatPearls Publishing. Retrieved 30 April 2022.
  5. ↑ Noda T (2011). "Native morphology of influenza virions". Frontiers in Microbiology. 2: 269. doi:10.3389/fmicb.2011.00269. PMC 3249889. PMID 22291683.
  6. ↑ Sugita Y, Noda T, Sagara H, Kawaoka Y (November 2011). "Ultracentrifugation deforms unfixed influenza A virions". The Journal of General Virology. 92 (Pt 11): 2485–93. doi:10.1099/vir.0.036715-0. PMC 3352361. PMID 21795472.
  7. ↑ Dadonaite B, Vijayakrishnan S, Fodor E, Bhella D, Hutchinson EC (August 2016). "Filamentous influenza viruses". The Journal of General Virology. 97 (8): 1755–64. doi:10.1099/jgv.0.000535. PMC 5935222. PMID 27365089.
  8. ↑ Eisfeld, Amie J.; Neumann, Gabriele; Kawaoka, Yoshihiro (January 2015). "At the centre: influenza A virus ribonucleoproteins". Nature Reviews Microbiology. 13 (1): 28–41. doi:10.1038/nrmicro3367. PMID 25417656. Retrieved 2 May 2022.
  9. ↑ Dadonaite, B; Gilbertson, B; Knight, ML; Trifkovic, S; Rockman, S; Laederach, A; Brown, LE; Fodor, E; Bauer, DLV (November 2019). "The structure of the influenza A virus genome". Nature microbiology. 4 (11): 1781–1789. doi:10.1038/s41564-019-0513-7. PMID 31332385. Retrieved 2 May 2022.
  10. ↑ Suarez DL, Spackman E, Senne DA, Bulaga L, Welsch AC, Froberg K (2003). "The effect of various disinfectants on detection of avian influenza virus by real time RT-PCR". Avian Diseases. 47 (3 Suppl): 1091–5. doi:10.1637/0005-2086-47.s3.1091. PMID 14575118. S2CID 8612187.
  11. ↑ "Avian Influenza (Bird Flu) Implications for Human Disease. Physical characteristics of influenza A viruses". CIDRAP - Center for Infectious Disease Research and Policy. University of Minnesota.
  12. ↑ "Flu viruses 'can live for decades' on ice". The New Zealand Herald. Reuters. November 30, 2006. Retrieved November 1, 2011.
  13. ↑ Wagner R, Matrosovich M, Klenk H (May–Jun 2002). "Functional balance between haemagglutinin and neuraminidase in influenza virus infections". Rev Med Virol. 12 (3): 159–66. doi:10.1002/rmv.352. PMID 11987141. S2CID 30876482.
  14. ↑ Lakadamyali M, Rust M, Babcock H, Zhuang X (Aug 5, 2003). "Visualizing infection of individual influenza viruses". Proc Natl Acad Sci USA. 100 (16): 9280–85. Bibcode:2003PNAS..100.9280L. doi:10.1073/pnas.0832269100. PMC 170909. PMID 12883000.
  15. ↑ Barry RD (August 1961). "The multiplication of influenza virus. II. Multiplicity reactivation of ultraviolet irradiated virus". Virology. 14 (4): 398–405. doi:10.1016/0042-6822(61)90330-0. hdl:1885/109240. PMID 13687359.
  16. ↑ Henle W, Liu OC (October 1951). "Studies on host-virus interactions in the chick embryo-influenza virus system. VI. Evidence for multiplicity reactivation of inactivated virus". The Journal of Experimental Medicine. 94 (4): 305–22. doi:10.1084/jem.94.4.305. PMC 2136114. PMID 14888814.
  17. ↑ Gilker JC, Pavilanis V, Ghys R (June 1967). "Multiplicity reactivation in gamma irradiated influenza viruses". Nature. 214 (5094): 1235–7. Bibcode:1967Natur.214.1235G. doi:10.1038/2141235a0. PMID 6066111. S2CID 4200194.
  18. ↑ "Multiplicity Reactivation". Encyclopedia of Genetics, Genomics, Proteomics and Informatics. Springer Netherlands. 2008. pp. 1289–1289. doi:10.1007/978-1-4020-6754-9_10950. Retrieved 4 May 2022.
  19. ↑ "1918 Pandemic (H1N1 virus) | Pandemic Influenza (Flu) | CDC". www.cdc.gov. 16 June 2020. Retrieved 6 May 2022.
  20. ↑ Jilani, Talha N.; Jamil, Radia T.; Siddiqui, Abdul H. (2022). "H1N1 Influenza". StatPearls. StatPearls Publishing. Retrieved 6 May 2022.
  21. ↑ "1957-1958 Pandemic (H2N2 virus) | Pandemic Influenza (Flu) | CDC". www.cdc.gov. 22 January 2019. Retrieved 6 May 2022.
  22. ↑ Tam, John S. (15 May 2002). "Influenza A (H5N1) in Hong Kong: an overview". Vaccine. 20 Suppl 2: S77–81. doi:10.1016/s0264-410x(02)00137-8. ISSN 0264-410X. Retrieved 6 May 2022.
  23. ↑ International Committee on Taxonomy of Viruses (2002). "46.0.1. Influenzavirus A". Archived from the original on 2004-12-07. Retrieved 2006-04-17.
  24. ↑ "New bird flu strain in China "one of the most lethal" warns WHO". MercoPress. Archived from the original on 14 May 2013. Retrieved 2020-12-06.
  25. ↑ Boston, 677 Huntington Avenue; Ma 02115 +1495‑1000 (2013-10-24). "Making the leap". News. Archived from the original on 3 January 2021. Retrieved 2020-12-06.
  26. ↑ Ungchusak, Kumnuan; Auewarakul, Prasert; Dowell, Scott F.; Kitphati, Rungrueng; Auwanit, Wattana; Puthavathana, Pilaipan; Uiprasertkul, Mongkol; Boonnak, Kobporn; Pittayawonganon, Chakrarat; Cox, Nancy J.; Zaki, Sherif R. (2005-01-27). "Probable Person-to-Person Transmission of Avian Influenza A (H5N1)". New England Journal of Medicine. 352 (4): 333–340. doi:10.1056/NEJMoa044021. ISSN 0028-4793. PMID 15668219. Archived from the original on 21 August 2020. Retrieved 22 April 2022.
  27. ↑ Komadina N, McVernon J, Hall R, Leder K (2014). "A historical perspective of influenza A(H1N2) virus". Emerg Infect Dis. 20 (1): 6–12. doi:10.3201/eid2001.121848. PMC 3884707. PMID 24377419.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  28. ↑ Mahmoud 2005, p. 7
  29. ↑ Detailed chart of its evolution here Archived 9 May 2009 at the Wayback Machine at PDF called Ecology and Evolution of the Flu
  30. ↑ Mahmoud 2005, p. 115
  31. ↑ Iuliano AD, Roguski KM, Chang HH, Muscatello DJ, Palekar R, Tempia S, Cohen C, Gran JM, Schanzer D, Cowling BJ, Wu P, Kyncl J, Ang LW, Park M, Redlberger-Fritz M, Yu H, Espenhain L, Krishnan A, Emukule G, van Asten L, Pereira da Silva S, Aungkulanon S, Buchholz U, Widdowson MA, Bresee JS (March 2018). "Estimates of global seasonal influenza-associated respiratory mortality: a modelling study". Lancet. 391 (10127): 1285–1300. doi:10.1016/s0140-6736(17)33293-2. PMC 5935243. PMID 29248255.
  32. ↑ Daum LT, Shaw MW, Klimov AI, Canas LC, Macias EA, Niemeyer D, Chambers JP, Renthal R, Shrestha SK, Acharya RP, Huzdar SP, Rimal N, Myint KS, Gould P (August 2005). "Influenza A (H3N2) outbreak, Nepal". Emerging Infectious Diseases. 11 (8): 1186–91. doi:10.3201/eid1108.050302. PMC 3320503. PMID 16102305.
  33. ↑ Taubenberger JK, Morens DM (January 2006). "1918 Influenza: the mother of all pandemics". Emerging Infectious Diseases. 12 (1): 15–22. doi:10.3201/eid1201.050979. PMC 3291398. PMID 16494711.
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