title: Epidemiological study of influenza B in Shanghai during the 2009-2014 seasons: implications for influenza vaccination strategy.
abstract: A new quadrivalent influenza vaccine has been available for influenza B, which can pose a significant global health burden. Shanghai has the highest GDP and largest metropolitan population in China. To understand the impact of influenza B in Shanghai in terms of age-related incidence and relative prevalence compared with other subtypes, we conducted this retrospective epidemiological study of influenza B in the 2009-2014 seasons. A total of 71 354 outpatients with influenza-like illness were included, and both lineages of influenza B and subtypes of influenza A were identified using real-time RT-PCR. The antigenic characteristics of influenza B isolates were analysed by sequencing and reciprocal haemagglutinin inhibition assay. On average, 33.45% of influenza strains were influenza B, and 40.20% of strains isolated from children were influenza B. The incidence of influenza B was highest (12.52 per 100 people with influenza-like illness) in children ages 6-17 years and usually peaked in this age group at the early stage of an influenza B epidemic. Overall, both matched and mismatched influenza B strains co-circulated in Shanghai annually, and 44.57% of the circulating influenza B belonged to the opposite lineage of the vaccine strains. We concluded that influenza B has caused a substantial impact in Shanghai and that school-aged children play a key role in the transmission of influenza B. Hence, it may be beneficial to prioritize influenza vaccination for school-aged children to mitigate the outbreaks of influenza B.
authors.affiliation: Bio-X Institutes, Shanghai Jiao Tong University, Shanghai, China; Shanghai Municipal Center for Disease Control and Prevention, Shanghai, China.
authors.forename: B
authors.initials: B
authors.lastname: Zhao
authors.affiliation: Bio-X Institutes, Shanghai Jiao Tong University, Shanghai, China.
authors.forename: S
authors.initials: S
authors.lastname: Qin
authors.affiliation: Shanghai Municipal Center for Disease Control and Prevention, Shanghai, China.
authors.forename: Z
authors.initials: Z
authors.lastname: Teng
authors.affiliation: Shanghai Municipal Center for Disease Control and Prevention, Shanghai, China.
authors.forename: J
authors.initials: J
authors.lastname: Chen
authors.affiliation: Shanghai Municipal Center for Disease Control and Prevention, Shanghai, China.
authors.forename: X
authors.initials: X
authors.lastname: Yu
authors.affiliation: Shanghai Municipal Center for Disease Control and Prevention, Shanghai, China.
authors.forename: Y
authors.initials: Y
authors.lastname: Gao
authors.affiliation: Shanghai Municipal Center for Disease Control and Prevention, Shanghai, China.
authors.forename: J
authors.initials: J
authors.lastname: Shen
authors.affiliation: Shanghai Municipal Center for Disease Control and Prevention, Shanghai, China.
authors.forename: X
authors.initials: X
authors.lastname: Cui
authors.affiliation: Department of Infectious Diseases, Children's Hospital of Fudan University, Shanghai, China. Electronic address: zengmeigao@aliyun.com.
authors.forename: M
authors.initials: M
authors.lastname: Zeng
authors.affiliation: Shanghai Municipal Center for Disease Control and Prevention, Shanghai, China. Electronic address: Zhangxi@scdc.sh.cn.
authors.forename: X
authors.initials: X
authors.lastname: Zhang
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D002681:China / Q000453:epidemiology; D016021:Epidemiologic Studies; D005260:Female; D006385:Hemagglutination Inhibition Tests; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D009981:Influenza B virus / Q000302:isolation & purification*; D007252:Influenza Vaccines / Q000008:administration & dosage* / Q000276:immunology*; D007251:Influenza, Human / Q000453:epidemiology* / Q000821:virology*; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D060888:Real-Time Polymerase Chain Reaction; D012189:Retrospective Studies; D020133:Reverse Transcriptase Polymerase Chain Reaction; D055815:Young Adult
chemical_list: D007252:Influenza Vaccines
keywords: Epidemiology; influenza B; lineage; school-aged children; vaccination