Stephen Kissler: Identifying the geographic transmission hubs of the 2009 A/H1N1pdm influenza pandemic in the United States

Conventional wisdom suggests that invasion waves of infection are likely to establish first in densely-populated, well-connected areas. We challenge this assumption in the context of the 2009 A/H1N1pdm influenza pandemic in the United States. Using a mechanistic spatial transmission model fit to a massive medical claims dataset, we identify four key geographic establishment sites, or "hubs", of the major autumn wave of the 2009 influenza pandemic in the US. Counter-intuitively, the hubs do not coincide with large and well-connected cities, indicating that factors beyond population density and travel volume are necessary to explain the outbreak's establishment sites. This work has been conducted in collaboration with Julia Gog, Cecile Viboud, Vivek Charu, Ottar Bjornstad, Lone Simonsen, and Bryan Grenfell.