A huge discrepancy occurred between Google Flu Trend and data collected by the CDC.
Scientific hindsight shows that Google Flu Trends far overstated this year's flu season, raising questions about the accuracy of using a search engine, which Google and the media hyped as an efficient public health tool, to accurately monitor the flu.
Nature's Declan Butler reported today on the huge discrepancy between Google Flu Trend's estimated peak flu levels and data collected by the U.S. Centers for Disease Control and Prevention (CDC) earlier this winter. Google bases their numbers on flu-related searches (the basic idea being that more people Googling terms like "flu symptoms" equals more people catching viruses). The CDC, on the other hand, uses traditional epidemiological surveillance methods. Past results have shown Google to have a pretty good track record on mirroring CDC flu charts. But this time, Google's algorithms doubled the CDC's (accurate) figues — overshooting the mark in some regions by an even higher margin.
There's no doubt that this year's flu season was severe. Outbreaks hit early and hard by any measure. CDC officials declared an influenza epidemic in early January, Boston's mayor called a public health emergency around the same time, and Chicago hospitals struggled to keep up with emergency room visits. Still, Google's alarming snapshot of over 10 percent of the U.S. population experiencing flu-like illness was nowhere near the actual peak of 6 percent incidence.