Nowcasting Influenza Incidence with CDC Web Traffic Data: A Demonstration Using a Novel Data Set

Influenza epidemics result in a public health and economic burden around the globe. Traditional surveillance techniques, which rely on doctor visits, provide data with a delay of 1-2 weeks. A means of obtaining real-time data and forecasting future outbreaks is desirable to provide more timely responses to influenza epidemics. In this work, we present the first implementation of a novel data set by demonstrating its ability to supplement traditional disease surveillance at multiple spatial resolutions. We use Internet traffic data from the Centers for Disease Control and Prevention (CDC) website to determine the potential usability of this data source. We test the traffic generated by ten influenza-related pages in eight states and nine census divisions within the United States and compare it against clinical surveillance data. Our results yield $r^2$ = 0.955 in the most successful case, promising results for some cases, and unsuccessful results for other cases. These results demonstrate that Internet data may be able to complement traditional influenza surveillance in some cases but not in others. Specifically, our results show that the CDC website traffic may inform national and division-level models but not models for each individual state. In addition, our results show better agreement when the data were broken up by seasons instead of aggregated over several years. In the interest of scientific transparency to further the understanding of when Internet data streams are an appropriate supplemental data source, we also include negative results (i.e., unsuccessful models). We anticipate that this work will lead to more complex nowcasting and forecasting models using this data stream.