title: Epidemiology of pandemic influenza A/H1N1 virus during 2009-2010 in Taiwan.
abstract: Outbreak of swine-origin influenza A/H1N1 virus (pdmH1N1) occurred in 2009. Taiwanese authorities implemented nationwide vaccinations with pdmH1N1-specific inactivated vaccine as of November 2009. This study evaluates prevalence, HA phylogenetic relationship, and transmission dynamic of influenza A and B viruses in Taiwan in 2009-2010. Respiratory tract specimens were analyzed for influenza A and B viruses. The pdmH1N1 peaked in November 2009, was predominant from August 2009 to January 2010, then sharply dropped in February 2010. Significant prevalence peaks of influenza B in April-June of 2010 and H3N2 virus in July and August were observed. Highest percentage of pdmH1N1- and H3N2-positive cases appeared among 11-15-year-olds; influenza B-positive cases were dominant among those 6-10 years old. Maximum likelihood phylogenetic trees showed 11 unique clusters of pdmH1N1, seasonal H3N2 influenza A and B viruses, as well as transmission clusters and mixed infections of influenza strains in Taiwan. The 2009 pdmH1N1 virus was predominant in Taiwan from August 2009 to January 2010; seasonal H3N2 influenza A and B viruses exhibited small prevalence peaks after nationwide vaccinations. Phylogenetic evidence indicated transmission clusters and multiple independent clades of co-circulating influenza A and B strains in Taiwan.
authors.affiliation: Department of Health Risk Management, School of Public, China Medical University, Taichung, Taiwan.
authors.forename: Yu-Ching
authors.initials: YC
authors.lastname: Lan
authors.forename: Mei-Chi
authors.initials: MC
authors.lastname: Su
authors.forename: Chao-Hsien
authors.initials: CH
authors.lastname: Chen
authors.forename: Su-Hua
authors.initials: SH
authors.lastname: Huang
authors.forename: Wan-Li
authors.initials: WL
authors.lastname: Chen
authors.forename: Ni
authors.initials: N
authors.lastname: Tien
authors.forename: Cheng-Wen
authors.initials: CW
authors.lastname: Lin
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D053118:Influenza A Virus, H1N1 Subtype / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D053122:Influenza A Virus, H3N2 Subtype / Q000145:classification / Q000276:immunology / Q000302:isolation & purification; D009980:Influenza A virus / Q000145:classification / Q000235:genetics / Q000302:isolation & purification; D009981:Influenza B virus / Q000145:classification / Q000235:genetics / Q000302:isolation & purification; D007251:Influenza, Human / Q000453:epidemiology / Q000821:virology*; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D058873:Pandemics; D010802:Phylogeny; D012621:Seasons; D013624:Taiwan / Q000453:epidemiology; D055815:Young Adult
keywords: HA subtyping; Mixed infection; Pandemic influenza; Phylogenetic analysis; Surveillance