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| {{Taxobox
| | #redirect [[Influenza]] |
| | name = Orthomyxoviridae
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| | virus_group = v
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| | familia = '''''Orthomyxoviridae'''''
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| | subdivision_ranks = Genera
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| | subdivision = ''[[Influenzavirus A]]''<br>
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| ''[[Influenzavirus B]]''<br>
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| ''[[Influenzavirus C]]''<br>
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| ''[[Isavirus]]''<br>
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| ''[[Thogotovirus]]
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| }}
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| {{SI}}
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| __NOTOC__
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| ==Overview==
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| '''Influenzavirus B''' is a genus in the [[virus]] family [[Orthomyxoviridae]]. The only species in this genus is called "Influenza B virus".
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| Influenza B viruses are only known to infect [[human]]s and [[Pinniped|seal]]s,<ref name="pmid10807575">{{cite journal | author = Osterhaus AD, Rimmelzwaan GF, Martina BE, Bestebroer TM, Fouchier RA | title = Influenza B virus in seals | journal = Science | volume = 288 | issue = 5468 | pages = 1051-3 | year = 2000 | pmid = 10807575 | doi = | issn = }}</ref> giving them [[influenza]]. This limited host 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 genetic drift and reassortment.<ref name="pmid11779385">{{cite journal | author = Hay AJ, Gregory V, Douglas AR, Lin YP | title = The evolution of human influenza viruses | journal = Philos. Trans. R. Soc. Lond., B, Biol. Sci. | volume = 356 | issue = 1416 | pages = 1861-70 | year = 2001 | pmid = 11779385 | doi = 10.1098/rstb.2001.0999}}</ref><ref name="pmid15258979">{{cite journal | author = Matsuzaki Y, Sugawara K, Takashita E, Muraki Y, Hongo S, Katsushima N, Mizuta K, Nishimura H | title = Genetic diversity of influenza B virus: the frequent reassortment and cocirculation of the genetically distinct reassortant viruses in a community | journal = J. Med. Virol. | volume = 74 | issue = 1 | pages = 132-40 | year = 2004 | pmid = 15258979 | doi = 10.1002/jmv.20156}}</ref><ref name="pmid10196339">{{cite journal | author = Lindstrom SE, Hiromoto Y, Nishimura H, Saito T, Nerome R, Nerome K | title = 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 | journal = J. Virol. | volume = 73 | issue = 5 | pages = 4413-26 | year = 1999 | pmid = 10196339 | doi = }}</ref> | |
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| Further diminishing the impact of this virus "in man, influenza B viruses evolve slower than A viruses and faster than C viruses".<ref name="pmid3267218">{{cite journal | author = Yamashita M, Krystal M, Fitch WM, Palese P | title = Influenza B virus evolution: co-circulating lineages and comparison of evolutionary pattern with those of influenza A and C viruses | journal = Virology | volume = 163 | issue = 1 | pages = 112-22 | year = 1988 | pmid = 3267218 | doi = }}</ref> Influenzavirus B mutates at a rate 2-3 times lower than type A.<ref>{{cite journal | author = Nobusawa E, Sato K | title = Comparison of the mutation rates of human influenza A and B viruses. | journal = J Virol | volume = 80 | issue = 7 | pages = 3675-8 | year = 2006 | month=Apr | id = PMID 16537638}}</ref> However, influenza B mutates enough that lasting immunity is not possible. For example at the [[United States|U.S.]]'s [[Food and Drug Administration]]'s (FDA) [[Center for Biologics Evaluation and Research]]'s Vaccines and Related Biological Products Advisory Committee's 101st meeting of February 16 2005, an extensive discussion and vote was held concerning next year's flu vaccine virus selection including which influenza B strain to use in the formulation of the flu vaccine:
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| <blockquote>"For [[Influenza B]], the question was asked: are there new strains present? And the answer was yes, and in 2004, the majority of the viruses were similar to a strain called B/Shanghai/361/2002, which is from the so-called B/Yamagata/1688 [[hemagglutinin]] lineage. That lineage was not the one that was being used in the vaccine that was current last year. In a minority of the strains that were found during the epidemiological studies were similar to the strain that was in the vaccine for last year, which was B/Hong Kong/330/2001, which belongs to the HA lineage that we represent with the strain B/Victoria/287. In answer to the question were these new viruses spreading, the answer, of course, is definitely yes. The Fujian-like viruses had become widespread around the world and were predominant everywhere, and these B/Shanghai-like strains at the time we were holding this meeting in February were predominant not only in North America and the United States, but also in Asia and Europe."<ref>Transcript of U.S. FDA Center for Biologics Evaluation and Research Vaccines and Related Biological Products Advisory Committee's 101st meeting of February 16, 2005. [http://origin.www.fda.gov/ohrms/dockets/ac/05/transcripts/2005-4087T1.DOC origin.www.fda.gov DOC format] [http://www.google.com/search?q=cache:8hPXwU4pfyAJ:origin.www.fda.gov/ohrms/dockets/ac/05/transcripts/2005-4087T1.DOC+CDC+H5N1+research+%22two+clades%22&hl=en&gl=us&ct=clnk&cd=18 Google provided HTML format]</ref></blockquote>
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| ==Morphology==
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| 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]].<ref name="ICTVdb">{{cite web | url = http://www.ncbi.nlm.nih.gov/ICTVdb/ICTVdB/00.046.0.04.htm | title = ICTVdB Virus Description - 00.046.0.04. Influenzavirus B | accessdate = 2007-09-15 | author = Büchen-Osmond, C. (Ed) | date = 2006 | format = | work = ICTVdB - The Universal Virus Database, version 4 | publisher = Columbia University, New York, USA }}</ref>
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| ==Nucleic Acid==
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| The Influenza B virus genome is 14648 [[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.<ref name="ICTVdb"/>
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| ==Sources==
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| {{reflist}}
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| ==Further reading==
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| * {{cite web | url = http://www.cdc.gov/ncidod/EID/vol11no08/05-0302.htm | title = Influenza A (H3N2) Outbreak, Nepal | accessdate = 2007-09-15 | author = Daum LT, Shaw MW, Klimov AI, Canas LC, Macias EA, Niemeyer D, et al. | date = [[2005-07-21]] | work = Emerg Infect Dis | publisher = Centers for Disease Control and Prevention}}
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| * {{cite journal | author = Nakagawa N, Nukuzuma S, Haratome S, Go S, Nakagawa T, Hayashi K | title = Emergence of an influenza B virus with antigenic change | journal = J. Clin. Microbiol. | volume = 40 | issue = 8 | pages = 3068-70 | year = 2002 | pmid = 12149383 | doi = 10.1128/JCM.40.8.3068-3070.2002 }}
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| {{Influenza}}
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| [[es:Influenzavirus B]]
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| [[Category:Viruses]]
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| [[Category:Influenza]]
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| [[Category:Infectious disease]]
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