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Google Flu Trends Not Accurate, Still Good Tool


Google Flu Trends was launched last year to provide estimates of flu activity for about 15 countries around the world. Information is provided by estimates based on aggregated search queries, some of which are validated with official data from agencies such as the US Centers for Disease Control. This week, a study presented at the ATS 2010 International Conference has found that Google Flu Trends was 25% less accurate at estimating rates of laboratory-confirmed influenza virus infection.

Read: Google Can Help Find Flu Vaccine, November 2009

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The researchers analyzed the incidence of flu outbreaks in the United States between 2003 and 2008 that were laboratory confirmed by the CDC and compared them to Google Flu Trends data. Although the website did not accurately reflect influenza activity, study leader Justin Ortiz MD, clinical fellow at the University of Washington, said that the data is highly correlated with non-specific syndrome of influenza-like illness, such as cough or sore throat.

Dr. Ortiz went on to say, "Many respiratory virus infections other than influenza can result in influenza-like illness. Furthermore, there is a wide and unpredictable proportion of influenza-like illness that is due to actual influenza virus. Because Google Flu Trends estimates of influenza-like illness may not necessarily correlate with actual influenza virus infections, we undertook this study to evaluate the validity of Google Flu Trends influenza surveillance by comparing it to a gold standard of CDC's national surveillance for influenza laboratory tests positive."

Even though the data is not considered accurate, Dr. Ortiz acknowledges that “Google Flu Trends provides an excellent public health service, because it provides nationwide influenza activity data in a cheap and timely manner.”

Seasonal flu epidemics account for as many as a half a million deaths in the world each year, and the rapid spread of new strains, such as the 2009 H1N1 flu pandemic, can cause many more. Quickly detecting a regional rise in flu-like symptoms can help public health officials take action to reduce the impact.