Detect Influenza outbreaks with web searches

Google have created a service to "Explore flu trends across the U.S.". The system tracks the use of search terms which indicate that people have influenza and plots this on a graph over time and a map of the USA. According to "Google Uses Searches to Track Flu’s Spread" (By MIGUEL HELFT, The New York Times, November 11, 200), a paper on this will be published in Nature.The idea of using web searches to detect natural phenomena is not a new one, with previous proposals to use internet traffic to detect earthquakes. The technique might be used as part of an ICT system to deal with an Avian Influenza Pandemic.

Each week, millions of users around the world search for online health information. As you might expect, there are more flu-related searches during flu season, more allergy-related searches during allergy season, and more sunburn-related searches during the summer. You can explore all of these phenomena using Google Trends. But can search query trends provide an accurate, reliable model of real-world phenomena?

We have found a close relationship between how many people search for flu-related topics and how many people actually have flu symptoms. Of course, not every person who searches for "flu" is actually sick, but a pattern emerges when all the flu-related search queries from each state and region are added together. We compared our query counts with data from a surveillance system managed by the U.S. Centers for Disease Control and Prevention (CDC) and discovered that some search queries tend to be popular exactly when flu season is happening. By counting how often we see these search queries, we can estimate how much flu is circulating in various regions of the United States. ...

From: How does this work?, Google Flu Trends, Google, 2008