Influenza B virus (IBV), belonging to the family Orthomyxoviridae, is a significant pathogen causing respiratory diseases in humans. First isolated and identified from clinical patients in 1940[1], children and the elderly are its primary susceptible populations. Compared to influenza A viruses, IBV was historically considered to cause milder clinical symptoms, exhibit lower antigenic specificity, and rarely trigger large-scale epidemics, leading to its frequent underestimation. Recent studies indicate that the harm caused by influenza B is nearly comparable to that of influenza A, with one-third of global influenza-related disease burden annually attributable to IBV infections[2].
The genome of IBV comprises eight segmented single-stranded negative-sense RNA molecules, collectively encoding at least 11 proteins, including polymerase subunits (PB2, P1, PA), hemagglutinin (HA), nucleoprotein (NP), neuraminidase (NA and NB), matrix proteins (M1 and BM2), and non-structural proteins (NS1 and NS2). Notably, NB and NA are unique to influenza B virus[3].
IBV is not categorized into subtypes but is divided into two major lineages based on antigenic characteristics and nucleotide sequences of the HA gene: B/Victoria/2/87-like (B/Victoria) and B/Yamagata/16/88-like (B/Yamagata). Since 2002, these two lineages have co-circulated worldwide[4, 5]. Current research shows differences in reassortment patterns between these lineages, with reassortment correlating to the relative genetic diversity of IBV[5]. Antigenic analysis reveals that the B/Yamagata lineage exhibits stronger genetic diversity than B/Victoria[6], potentially leading to higher susceptibility in patients infected with a B/Yamagata strain to co-circulating strains of the same lineage[7].
Samples collection date:
Samples host information:
Samples clade information:
[1] FRANCIS T, JR. A NEW TYPE OF VIRUS FROM EPIDEMIC INFLUENZA [J]. Science, 1940, 92(2392): 405-8.
[2] LANGAT P, RAGHWANI J, DUDAS G, et al. Genome-wide evolutionary dynamics of influenza B viruses on a global scale [J]. PLoS Pathog, 2017, 13(12): e1006749.
[3] KOUTSAKOS M, NGUYEN T H, BARCLAY W S, et al. Knowns and unknowns of influenza B viruses [J]. Future Microbiol, 2016, 11(1): 119-35.
[4] ZARAKET H, HURT A C, CLINCH B, et al. Burden of influenza B virus infection and considerations for clinical management [J]. Antiviral research, 2021, 185: 104970.
[5] VIRK R K, JAYAKUMAR J, MENDENHALL I H, et al. Divergent evolutionary trajectories of influenza B viruses underlie their contemporaneous epidemic activity [J]. Proc Natl Acad Sci U S A, 2020, 117(1): 619-28.
[6] YANG J, LAU Y C, WU P, et al. Variation in Influenza B Virus Epidemiology by Lineage, China [J]. Emerg Infect Dis, 2018, 24(8): 1536-40.
[7] 王宇茜, 温冬华. 乙型流感病毒的研究进展 [J]. 国际检验医学杂志, 2023, 44(12): 1517-1521.