Google flu trends: Web searches as sensors

April 26th, 2009

Google has had a special “flu trends” site up for many months that provides “up-to-date estimates of flu activity in the United States based on aggregated search queries.”

They have found that how many people search for flu-related topics is a leading indicator for reports on how many people actually have flu symptoms. They believe that this metric “may indicate flu activity up to two weeks ahead of traditional flu surveillance systems”. Click on the flash video below to see the relationship between the flu searches and flu symptoms.

So, is Google magic? The explanation for why changes in in the level of flu searches precedes changes in the level of flu symptoms is more mundane.

“So why bother with estimates from aggregated search queries? It turns out that traditional flu surveillance systems take 1-2 weeks to collect and release surveillance data, but Google search queries can be automatically counted very quickly. By making our flu estimates available each day, Google Flu Trends may provide an early-warning system for outbreaks of influenza.”

You can get the details in a recent article in nature:

J. Ginsberg, M. Mohebbi, R. Patel, L. Brammer, M. Smolinski and L. Brilliant, Detecting influenza epidemics using search engine query data, Nature 457, 1012-1014 (19 February 2009).

Of course, such leading indicators may not correlate well if there is a “black swan” flu epidemic or even if there is an unfounded fear of one. Sometimes the crowds are wise, but often not. Remember when we all thought technology stocks real estate was a good thing to invest in?

The Google site also allows you to look at the data by state as well. Click on the image below to try it out.