The purpose of Google Flu Trends (GFT) is to use search keyword trends from
Google.com to produce a daily estimate, or nowcast, of the occurrence of flu two
weeks in advance of publication of official surveillance data. While not covered in
detail in this paper, Google Dengue Trends, launched in June 2011, is a service
that uses similar techniques to track Dengue fever. During the 2012 flu season we
observed our algorithm overestimating influenza-like illness (ILI). We have
concluded that our algorithm for Flu and Dengue were susceptible to heightened
media coverage and have since developed several improvements.