Comparative Epidemiology of Influenza B Yamagata- and Victoria-Lineage Viruses in Households

Am J Epidemiol. 2015 Oct 15;182(8):705-13. doi: 10.1093/aje/kwv110. Epub 2015 Sep 22.


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.

Keywords: Victoria lineage; Yamagata lineage; disease transmission; influenza; influenza B virus.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Child
  • Child, Preschool
  • Family Characteristics*
  • Female
  • Follow-Up Studies
  • Hong Kong / epidemiology
  • Humans
  • Influenza B virus / classification*
  • Influenza B virus / isolation & purification
  • Influenza, Human / epidemiology*
  • Influenza, Human / mortality
  • Influenza, Human / virology*
  • Kaplan-Meier Estimate
  • Male
  • Middle Aged
  • Outpatients / statistics & numerical data*
  • Randomized Controlled Trials as Topic
  • Real-Time Polymerase Chain Reaction
  • Retrospective Studies