Phylogenetic and evolutionary history of influenza B viruses, which caused a large epidemic in 2011-2012, Taiwan.
The annual recurrence of the influenza epidemic is considered to be primarily associated with immune escape due to changes to the virus. In 2011-2012, the influenza B epidemic in Taiwan was unusually large, and influenza B was predominant for a long time. To investigate the genetic dynamics of influenza B viruses during the 2011-2012 epidemic, we analyzed the sequences of 4,386 influenza B viruses collected in Taiwan from 2004 to 2012. The data provided detailed insight into the flux patterns of multiple genotypes. We found that a re-emergent TW08-I virus, which was the major genotype and had co-circulated with the two others, TW08-II and TW08-III, from 2007 to 2009 in Taiwan, successively overtook TW08-II in March and then underwent a lineage switch in July 2011. This lineage switch was followed by the large epidemic in Taiwan. The whole-genome compositions and phylogenetic relationships of the representative viruses of various genotypes were compared to determine the viral evolutionary histories. We demonstrated that the large influenza B epidemic of 2011-2012 was caused by Yamagata lineage TW08-I viruses that were derived from TW04-II viruses in 2004-2005 through genetic drifts without detectable reassortments. The TW08-I viruses isolated in both 2011-2012 and 2007-2009 were antigenically similar, indicating that an influenza B virus have persisted for 5 years in antigenic stasis before causing a large epidemic. The results suggest that in addition to the emergence of new variants with mutations or reassortments, other factors, including the interference of multi-types or lineages of influenza viruses and the accumulation of susceptible hosts, can also affect the scale and time of an influenza B epidemic.
Centers for Disease Control, Taipei, Taiwan, Republic of China.
Ji-Rong
JR
Yang
Yuan-Pin
YP
Huang
Feng-Yee
FY
Chang
Li-Ching
LC
Hsu
Yu-Cheng
YC
Lin
Hsiang-Yi
HY
Huang
Fu-Ting
FT
Wu
Ho-Sheng
HS
Wu
Ming-Tsan
MT
Liu
D001483:Base Sequence; D058872:Epidemics; D019143:Evolution, Molecular; D005838:Genotype; D006801:Humans; D009981:Influenza B virus / Q000235:genetics* / Q000302:isolation & purification; D007251:Influenza, Human / Q000453:epidemiology* / Q000821:virology; D008969:Molecular Sequence Data; D010802:Phylogeny; D015995:Prevalence; D012367:RNA, Viral / Q000737:chemistry; D017423:Sequence Analysis, RNA; D013624:Taiwan / Q000453:epidemiology
D012367:RNA, Viral