Google tracks flu trends across the U.S.

I'm sensitive to concerns about the collection of user data on the Internet, but Google's new flu-trends tool is really amazing.

Google teamed up with the Centers for Disease Control last year to track Web searches on flu-related topics and found a close relationship between those searches and actual occurrences of flu symptoms. That is, people who are already sick are more likely to look up the word "flu"or flu-related topics on the Web. The data from Google users actually came very close to the flu activity indicator used by the CDC. The big difference? The Google data was available up to two weeks earlier than the published CDC reports. Now Google is making public its flu trends data in real time for the 2008-2009 flu season, with the caveat that "past performance is no guarantee of future results."

Here are today's flu trends in the U.S (click on image to enlarge).

We'll see if this season's flu trends match last year's performance, but I for one will be checking this tool before I fly home for the holidays.

For more on preventing and treating the flu, see our latest flu shot report, as well as our full condition coverage of the flu.

—Kevin McCarthy, associate editor