title: Comparative Epidemiology of Influenza B Yamagata- and Victoria-Lineage Viruses in Households.
abstract: Influenza B viruses split into 2 distinct lineages in the early 1980s, commonly named the Victoria and Yamagata lineages. There are few data on the comparative epidemiology of Victoria- and Yamagata-lineage viruses. In 2007-2011, we enrolled 75 and 34 households containing index patients with acute respiratory illness who tested positive for Yamagata- and Victoria-lineage viruses, respectively, from outpatient clinics in Hong Kong, China. These index patients and their household contacts were followed up for 7-10 days. We examined overall risk of polymerase chain reaction-confirmed infection among household contacts and the risk of secondary infection within households using an individual-based hazard model that accounted for tertiary transmission and infections occurring outside the household. We found that for Victoria-lineage viruses, the risk of within-household infection among household contacts aged ≤15 years was significantly higher (risk ratio = 12.9, 95% credibility interval: 4.2, 43.6) than that for older household contacts, while for Yamagata-lineage viruses, the risk of within-household infection for household contacts did not differ by age. Influenza B Yamagata- and Victoria-lineage viruses have similar characteristics in terms of viral shedding and clinical illness. The mechanisms underlying these epidemiologic differences deserve further investigation.
authors.forename: Cuiling
authors.initials: C
authors.lastname: Xu
authors.forename: Kwok-Hung
authors.initials: KH
authors.lastname: Chan
authors.forename: Tim K
authors.initials: TK
authors.lastname: Tsang
authors.forename: Vicky J
authors.initials: VJ
authors.lastname: Fang
authors.forename: Rita O P
authors.initials: RO
authors.lastname: Fung
authors.forename: Dennis K M
authors.initials: DK
authors.lastname: Ip
authors.forename: Simon
authors.initials: S
authors.lastname: Cauchemez
authors.forename: Gabriel M
authors.initials: GM
authors.lastname: Leung
authors.forename: J S Malik
authors.initials: JS
authors.lastname: Peiris
authors.forename: Benjamin J
authors.initials: BJ
authors.lastname: Cowling
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D005191:Family Characteristics; D005260:Female; D005500:Follow-Up Studies; D006723:Hong Kong / Q000453:epidemiology; D006801:Humans; D009981:Influenza B virus / Q000145:classification* / Q000302:isolation & purification; D007251:Influenza, Human / Q000453:epidemiology* / Q000401:mortality / Q000821:virology*; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D010045:Outpatients / Q000706:statistics & numerical data*; D016032:Randomized Controlled Trials as Topic; D060888:Real-Time Polymerase Chain Reaction; D012189:Retrospective Studies
keywords: Victoria lineage; Yamagata lineage; disease transmission; influenza; influenza B virus