Onset of a pandemic: Characterizing the initial phase of the swine flu (H1N1) epidemic in Israel

Uri Roll, Rami Yaari, Guy Katriel, Oren Barnea, Lewi Stone*, Ella Mendelson, Michal Mendelboim, Amit Huppert

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

16 Scopus citations


Background: The swine influenza H1N1 first identified in Mexico, spread rapidly across the globe and is considered the fastest moving pandemic in history. The early phase of an outbreak, in which data is relatively scarce, presents scientific challenges on key issues such as: scale, severity and immunity which are fundamental for establishing sound and rapid policy schemes. Our analysis of an Israeli dataset aims at understanding the spatio-temporal dynamics of H1N1 in its initial phase.Methods: We constructed and analyzed a unique dataset from Israel on all confirmed cases (between April 26 to July 7, 2009), representing most swine flu cases in this period. We estimated and characterized fundamental epidemiological features of the pandemic in Israel (e.g. effective reproductive number, age-class distribution, at-risk social groups, infections between sexes, and spatial dynamics). Contact data collected during this stage was used to estimate the generation time distribution of the pandemic.Results: We found a low effective reproductive number (Re = 1.06), an age-class distribution of infected individuals (skewed towards ages 18-25), at-risk social groups (soldiers and ultra Orthodox Jews), and significant differences in infections between sexes (skewed towards males). In terms of spatial dynamics, the pandemic spread from the central coastal plain of Israel to other regions, with higher infection rates in more densely populated sub-districts with higher income households.Conclusions: Analysis of high quality data holds much promise in reducing uncertainty regarding fundamental aspects of the initial phase of an outbreak (e.g. the effective reproductive number Re, age-class distribution, at-risk social groups). The formulation for determining the effective reproductive number Re used here has many advantages for studying the initial phase of the outbreak since it neither assumes exponential growth of infectives and is independent of the reporting rate. The finding of a low Re (close to unity threshold), combined with identification of social groups with high transmission rates would have enabled the containment of swine flu during the summer in Israel. Our unique use of contact data provided new insights into the differential dynamics of influenza in different ages and sexes, and should be promoted in future epidemiological studies. Thus our work highlights the importance of conducting a comprehensive study of the initial stage of a pandemic in real time.

Original languageEnglish
Article number92
JournalBMC Infectious Diseases
StatePublished - 14 Apr 2011


FundersFunder number
Israel National Institute for Health Policy and Health Services Research
Seventh Framework Programme231807
Israel Academy of Sciences and Humanities
Israel Science Foundation
Ministry of Health, State of Israel


    • Epidemiology H1N1
    • Pandemic influenza
    • swine-flu


    Dive into the research topics of 'Onset of a pandemic: Characterizing the initial phase of the swine flu (H1N1) epidemic in Israel'. Together they form a unique fingerprint.

    Cite this