Influenza B virus

The "'Influenza B virus"' is the only member of the genus "'Betainfluenzavirus"' in the virus family "Orthomyxoviridae". Influenza B virus is known to infect only humans and seals, distinguishing it from other influenza viruses, such as influenza A virus, which are capable of infecting a wider variety of hosts.

Influenza virus

Host range and lack of pandemics

It is believed that the narrow host range of the influenza B virus, which primarily infects humans and seals, is responsible for the absence of pandemics. This is in contrast to the influenza A virus, which has caused many pandemics and has a similar morphology. Both influenza A and B viruses mutate through antigenic drift and reassortment, although influenza B virus's narrow host range limits the likelihood of extensive transmission and epidemics.

Lineages

Based on the antigenic characteristics of the surface glycoprotein hemagglutinin, the influenza B virus is known to circulate in two lineages. These lineages are designated B/Yamagata/16/88-like and B/Victoria/2/87-like viruses. Co-circulation of these lineages adds to the evolution and total diversity of the influenza B virus.

Prevention and vaccination

The quadrivalent influenza vaccine licensed by the CDC is intended to provide protection against both co-circulating lineages of the influenza B virus and two strains of the influenza A virus. It has been demonstrated that the quadrivalent vaccine is more effective than the trivalent vaccine, which protects against only one influenza B lineage.

Treatment

Antiviral drugs such oseltamivir (Tamiflu), zanamivir (Relenza, and peramivir (Rapivab) can be used to treat influenza B virus infections. By blocking the viral neuraminidase enzyme, these drugs restrict the release of new virus particles from infected cells.

See also

• Influenza A virus
• Influenza vaccine
• Influenza pandemic

Summary

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. 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. 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.

References

• Chen R, Holmes EC. The evolutionary dynamics of human influenza B virus. J Mol Evol. 2008 Feb;66(2):655-63. doi: 10.1007/s00239-008-9089-x. PMID: 18274802.
• Rota PA, Wallis TR, Harmon MW, Rota JS, Kendal AP, Nerome K. Cocirculation of two distinct evolutionary lineages of influenza type B virus since 1983. Virology. 1990 Feb;174(2):361-73. doi: 10.1016/0042-6822(90)90086-9. PMID: 2154522.
• Belshe RB, Coelingh K, Ambrose CS, Woo JC, Wu X. Efficacy of live attenuated influenza vaccine in children against influenza B viruses by lineage and antigenic similarity. Vaccine. 2010 Feb 10;28(7):2149-56. doi: 10.1016/j.vaccine.2009.11.068. PMID: 20003924.

Further reading

• Lambert LC, Fauci AS. Influenza vaccines for the future. N Engl J Med. 2010 Nov 18;363(21):2036-44. doi: 10.1056/NEJMra1002842. PMID: 21083388.
• Paul Glezen W, Schmier JK, Kuehn CM, Ryan KJ, Oxford J. The burden of influenza B: a structured literature review. Am J Public Health. 2013 Mar;103(3):e43-51. doi: 10.2105/AJPH.2012.301137. PMID: 23327249.

External links

• Influenza (Flu) Viruses - CDC information page on influenza viruses, including Influenza B virus
• Influenza B virus evolution and its implications for vaccine strain selection - A review article discussing the evolutionary dynamics of influenza B virus and their implications for vaccine strain selection.

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