Google Flu Trends has been a critical tool for many trying to gauge the severity of influenza since it’s launch in 2008. Each year, Google Flu Trends attempts to show flu prevalence based off of flu-related Google search queries. Flu Trends has been quite accurate throughout its history… until this year.
Nature.com reports that Google Flu Trends overshot the percent of the U.S. population with influenza-like illness by nearly double what the CDC reported. But why? Well, for starters, the flu hit early this year. The peak of the flu outbreak occurred late December, something that isn’t very traditional. Here’s a look at 2012-13 (dark blue) versus previous years (lighter blue):
Additionally, this flu virus was extra potent as the Influenza Mortality rate was above the epidemic threshold, according to the CDC. The timing, and severity of the flu made for instant media fodder. Experts deemed this virus a particularly bad one. New York declared a Flu emergency. The monumental coverage of the flu this year likely led to Google being wrong… very wrong.
Speculation is that the widespread media attention and overall hullabaloo around this year’s flu simply caused more people to search the topic, causing Google to show incorrect estimates. This isn’t the first time this has happened, either. Back in 2009, Google had to shift algorithms when the H1N1 virus (Swine Flu) hit due to incorrect search signals.
So, while Google Flu Trends can be a great source for determining chatter, it isn’t perfect. While Google didn’t give an official comment to Nature.com, look for more algorithm tweaks to occur to prevent this in the future.