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Science
Vol. 312 no. 5772 pp. 447-451
DOI: 10.1126/science.1125237
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Synchrony, Waves, and Spatial Hierarchies in the Spread of Influenza

  1. Bryan T. Grenfell1,3

+ Author Affiliations

  1. 1 Fogarty International Center, National Institutes of Health, Bethesda, MD 20892, USA.
  2. 2 Department of Entomology, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
  3. 3 Center for Infectious Disease Dynamics, Department of Biology, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
  4. 4 National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20818, USA.
  1. * To whom correspondence should be addressed. E-mail: viboudc@mail.nih.gov

Quantifying long-range dissemination of infectious diseases is a key issue in their dynamics and control. Here, we use influenza-related mortality data to analyze the between-state progression of interpandemic influenza in the United States over the past 30 years. Outbreaks show hierarchical spatial spread evidenced by higher pairwise synchrony between more populous states. Seasons with higher influenza mortality are associated with higher disease transmission and more rapid spread than are mild ones. The regional spread of infection correlates more closely with rates of movement of people to and from their workplaces (workflows) than with geographical distance. Workflows are described in turn by a gravity model, with a rapid decay of commuting up to around 100 km and a long tail of rare longer range flow. A simple epidemiological model, based on the gravity formulation, captures the observed increase of influenza spatial synchrony with transmissibility; high transmission allows influenza to spread rapidly beyond local spatial constraints.

  • Received for publication 23 January 2006.
  • Accepted for publication 20 March 2006.

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