Influenzavirus B

Virus classification
Group: Group V ((-)ssRNA)
Family: Orthomyxoviridae

Influenzavirus A
Influenzavirus B
Influenzavirus C

Influenzavirus B is a genus in the virus family Orthomyxoviridae. The only species in this genus is called Influenza B virus.

Influenza B viruses are only known to infect humans and seals,[1] giving them influenza. This limited host and range is apparently responsible for the lack of Influenzavirus B-caused influenza pandemics in contrast with those caused by the morphologically similar Influenzavirus A as both mutate by both antigenic drift and reassortment.[2][3][4] Currently there are two co-circulating lineages of the 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.[5] 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. [6]

Further diminishing the impact of this virus "in man, influenza B viruses evolve slower than A viruses and faster than C viruses".[7] Influenzavirus B mutates at a rate 2 to 3 times slower than type A.[8] It is currently accepted that influenza B viruses cause significant morbidity and mortality worldwide, and significantly impacts adolescents and schoolchildren. [9]


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.[10]

Genome structure

The Influenza B virus genome is 14548 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.[10]


Sources and notes

  1. Osterhaus AD, Rimmelzwaan GF, Martina BE, Bestebroer TM, Fouchier RA (2000). "Influenza B virus in seals". Science. 288 (5468): 1051–3. doi:10.1126/science.288.5468.1051. PMID 10807575.
  2. 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 1088562Freely accessible. PMID 11779385.
  3. 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.
  4. 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. PMC 104222Freely accessible. PMID 10196339.
  5. 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): 6461–6471. doi:10.1016/j.vaccine.2012.07.089.
  6. 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): 4092–4102. doi:10.1016/j.vaccine.2016.06.064.
  7. Yamashita M, Krystal M, Fitch WM, Palese P (1988). "Influenza B virus evolution: co-circulating lineages and comparison of evolutionary pattern with those of influenza A and C viruses". Virology. 163 (1): 112–22. doi:10.1016/0042-6822(88)90238-3. PMID 3267218.
  8. Nobusawa E, Sato K (April 2006). "Comparison of the Mutation Rates of Human Influenza A and B Viruses". J Virol. 80 (7): 3675–8. doi:10.1128/JVI.80.7.3675-3678.2006. PMC 1440390Freely accessible. PMID 16537638.
  9. 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): 1447–1465. doi:10.2217/fmb.15.65.
  10. 1 2 Büchen-Osmond, C. (Ed) (2006). "ICTVdB Virus Description— Influenzavirus B". ICTVdB—The Universal Virus Database, version 4. Columbia University, New York, USA. Retrieved 2007-09-15.
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