We evaluated four independent predictors for the date of first confirmed 2009 A/H1N1 case: the volume of (1) direct and (2) indirect passengers on international flights, (3) the country-specific Gross Domestic Product and (4) healthcare spending per capita, by both private and public entities, from 2006 (the most recent year with all data available) from World Bank estimates [32] . We also examined alternate socio-economic metrics as compiled by the World Bank [32] , such as the number of physicians, and average population density. However models including these predictors did not perform as well (as measured by AIC) and often had many more missing values if limited to most recent information.