Bolivia, Brazil, India, Indonesia and Singapore were chosen for analysis based on data availability and adequate search volume. For each country, a univariate linear model was built by fitting a time series of the fraction of Google search query volume for specific dengue-related queries from that country against a 'gold standard' time series of dengue case counts for a time-frame within 2003Á2010. The specific combination of queries used was chosen to maximize model fit. Spurious spikes in the data were also removed prior to model fitting. The final models, fit using a training subset of the data, were cross-validated against both the overall dataset and a holdout subset of the data. All search queries were fully anonymized. This methodology is similar to the approach used to develop Google flu trends (3) .