Influenza B virus

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Influenza B virus
Virion structure of influenza B virus
Virus classification e
(unranked): Virus
Realm: Riboviria
Kingdom: Orthornavirae
Phylum: Negarnaviricota
Class: Insthoviricetes
Order: Articulavirales
Family: Orthomyxoviridae
Genus: Betainfluenzavirus
Influenza B virus
  • Influenza type B virus[1]
  • Influenza virus B[2]
  • Influenzavirus B[3]

Influenza B virus is the only species in the genus Betainfluenzavirus in the virus family Orthomyxoviridae.

Influenza B virus is known only to infect humans and seals.[4] This limited host range is apparently responsible for the lack of associated influenza pandemics in contrast with those caused by the morphologically similar influenza A virus as both mutate by both antigenic drift and reassortment.[5][6][7] There are two known circulating lineages of Influenza B virus based on the antigenic properties of the surface glycoprotein hemagglutinin. The lineages are termed B/Yamagata/16/88-like and B/Victoria/2/87-like viruses.[8] The quadrivalent influenza vaccine licensed by the CDC is currently designed to protect against both co-circulating lineages and has been shown to have greater effectiveness in prevention of influenza caused by Influenza B virus than the previous trivalent vaccine.[9]

Further diminishing the impact of this virus, "in humans, influenza B viruses evolve slower than A viruses and faster than C viruses".[10] Influenzavirus B mutates at a rate 2 to 3 times slower than type A.[11] Nevertheless, it is accepted that Influenza B virus could cause significant morbidity and mortality worldwide, and significantly impacts adolescents and schoolchildren.[12]

The B/Yamagata lineage might have become extinct in 2020/2021 due to COVID-19 pandemic measures.[13][14]


The Influenza B virus capsid is enveloped while its virion consists of an envelope, a matrix protein, a nucleoprotein complex, a nucleocapsid, and a polymerase complex. It is sometimes spherical and sometimes filamentous. Its 500 or so surface projections are made of hemagglutinin and neuraminidase.[15]

Genome structure and genetics[edit]

The Influenza B virus genome is 14,548 nucleotides long and consists of eight segments of linear negative-sense, single-stranded RNA. The multipartite genome is encapsidated, each segment in a separate nucleocapsid, and the nucleocapsids are surrounded by one envelope.[15]

The subtypes of influenza A virus are estimated to have diverged 2,000 years ago. Influenza viruses A and B are estimated to have diverged from a single ancestor around 4,000 years ago, while the ancestor of influenza viruses A and B and the ancestor of influenza virus C are estimated to have diverged from a common ancestor around 8,000 years ago.[16] Metatranscriptomics studies have also identified closely related "Influenza B-like" viruses such as the Wuhan spiny eel influenza virus[17] and also "Influenza-B like" viruses in a number of vertebrate species such as salamanders and fish.[18]


  1. ^ ICTV 2nd Report Fenner, F. (1976). Classification and nomenclature of viruses. Second report of the International Committee on Taxonomy of Viruses. Intervirology 7: 1-115. p57
  2. ^ ICTV 6th Report Murphy, F. A., Fauquet, C. M., Bishop, D. H. L., Ghabrial, S. A., Jarvis, A. W. Martelli, G. P. Mayo, M. A. & Summers, M. D.(eds)(1995). Virus Taxonomy. Sixthreport of the International Committee on Taxonomy of Viruses. Archives of Virology Supplement 10, p297
  3. ^ Smith, Gavin JD; et al. (8 June 2017). "Changing individual genus and species names in the family Orthomyxoviridae". International Committee on Taxonomy of Viruses (ICTV). Retrieved 22 March 2019.
  4. ^ Osterhaus AD, Rimmelzwaan GF, Martina BE, Bestebroer TM, Fouchier RA (2000). "Influenza B virus in seals". Science. 288 (5468): 1051–53. Bibcode:2000Sci...288.1051O. doi:10.1126/science.288.5468.1051. PMID 10807575.
  5. ^ Hay AJ, Gregory V, Douglas AR, Lin YP (2001). "The evolution of human influenza viruses". Philos. Trans. R. Soc. Lond. B Biol. Sci. 356 (1416): 1861–70. doi:10.1098/rstb.2001.0999. PMC 1088562. PMID 11779385.
  6. ^ Matsuzaki Y, Sugawara K, Takashita E, Muraki Y, Hongo S, Katsushima N, Mizuta K, Nishimura H (2004). "Genetic diversity of influenza B virus: The frequent reassortment and cocirculation of the genetically distinct reassortant viruses in a community". J. Med. Virol. 74 (1): 132–40. doi:10.1002/jmv.20156. PMID 15258979. S2CID 31146117.
  7. ^ Lindstrom SE, Hiromoto Y, Nishimura H, Saito T, Nerome R, Nerome K (1999). "Comparative Analysis of Evolutionary Mechanisms of the Hemagglutinin and Three Internal Protein Genes of Influenza B Virus: Multiple Cocirculating Lineages and Frequent Reassortment of the NP, M, and NS Genes". J. Virol. 73 (5): 4413–26. doi:10.1128/JVI.73.5.4413-4426.1999. PMC 104222. PMID 10196339.
  8. ^ Klimov, Alexander I.; Garten, Rebecca; Russell, Colin; Barr, Ian G.; Besselaar, Terry G.; Daniels, Rod; Engelhardt, Othmar G.; Grohmann, Gary; Itamura, Shigeyuki; Kelso, Anne; McCauley, John; Odagiri, Takato; Smith, Derek; Tashiro, Masato; Xu, Xiyan; Webby, Richard; Wang, Dayan; Ye, Zhiping; Yuelong, Shu; Zhang, Wenqing; Cox, Nancy (October 2012). "WHO recommendations for the viruses to be used in the 2012 Southern Hemisphere Influenza Vaccine: Epidemiology, antigenic and genetic characteristics of influenza A(H1N1)pdm09, A(H3N2) and B influenza viruses collected from February to September 2011". Vaccine. 30 (45): 6461–71. doi:10.1016/j.vaccine.2012.07.089. PMC 6061925. PMID 22917957.
  9. ^ Moa, Aye M.; Chughtai, Abrar A.; Muscatello, David J.; Turner, Robin M.; MacIntyre, C. Raina (July 2016). "Immunogenicity and safety of inactivated quadrivalent influenza vaccine in adults: A systematic review and meta-analysis of randomised controlled trials". Vaccine. 34 (35): 4092–102. doi:10.1016/j.vaccine.2016.06.064. PMID 27381642.
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  11. ^ Nobusawa E, Sato K (April 2006). "Comparison of the Mutation Rates of Human Influenza A and B Viruses". J Virol. 80 (7): 3675–78. doi:10.1128/JVI.80.7.3675-3678.2006. PMC 1440390. PMID 16537638.
  12. ^ van de Sandt, Carolien E; Bodewes, Rogier; Rimmelzwaan, Guus F; de Vries, Rory D (September 2015). "Influenza B viruses: not to be discounted". Future Microbiology. 10 (9): 1447–65. doi:10.2217/fmb.15.65. PMID 26357957.
  13. ^ Alhoufie, Sari T.; Alsharif, Naif H.; Alfarouk, Khalid O.; Ibrahim, Nadier A.; Kheyami, Ali M.; Aljifri, Alanoud A. (November 2021). "COVID-19 with underdiagnosed influenza B and parainfluenza-2 co-infections in Saudi Arabia: Two case reports". Journal of Infection and Public Health. 14 (11): 1567–1570. doi:10.1016/j.jiph.2021.09.005. PMC 8442300. PMID 34627054.
  14. ^ Koutsakos, Marios; Wheatley, Adam K.; Laurie, Karen; Kent, Stephen J.; Rockman, Steve (December 2021). "Influenza lineage extinction during the COVID-19 pandemic?". Nature Reviews Microbiology. 19 (12): 741–742. doi:10.1038/s41579-021-00642-4. PMC 8477979. PMID 34584246.
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  17. ^ Shi M, Lin XD, Chen X, Tian JH, Chen LJ, Li K; et al. (2018). "The evolutionary history of vertebrate RNA viruses". Nature. 556 (7700): 197–202. Bibcode:2018Natur.556..197S. doi:10.1038/s41586-018-0012-7. PMID 29618816. S2CID 4608233.{{cite journal}}: CS1 maint: multiple names: authors list (link)
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