Modelling the spatial-temporal progression of the 2009 A/H1N1 influenza pandemic in Chile

spatial-temporal transmission model of 2009 A/H1N1 pandemic inuenza across Chile, a country that spans a large latitudinal range, is devel-oped to characterize the spatial variation in peak timing of that pandemic as a function of local transmission rates, spatial connectivity assumptions for Chilean regions, and the putative location of introduction of the novel virus into the country. Speciffcally, a metapopulation SEIR (susceptible-exposed-infected-removed) compartmental model that tracks the transmission dynam-ics of inuenza in 15 Chilean regions is calibrated. The model incorporates population mobility among neighboring regions and indirect mobility to and from other regions via the metropolitan central region ("hub region"). The stability of the disease-free equilibrium of this model is analyzed and com-pared with the corresponding stability in each region, concluding that stability may occur even with some regions having basic reproduction numbers above 1. The transmission model is used along with epidemiological data to explore potential factors that could have driven the spatial-temporal progression of the pandemic. Simulations and sensitivity analyses indicate that this relatively simple model is suffcient to characterize the south-north gradient in peak timing observed during the pandemic, and suggest that south Chile observed the initial spread of the pandemic virus, which is in line with a retrospective epidemiological study. The "hub region" in our model signiffcantly enhanced population mixing in a short time scale.