(Cross-posted on the Official Google Blog)
In November 2008 we launched Google Flu Trends after finding a close relationship between how many people search for flu-related topics and how many people actually have flu symptoms. Google Flu Trends may be able to detect influenza outbreaks earlier than other systems because it estimates flu activity in near real time.
In response to recent inquiries from public health officials, we've been attempting to use Google search activity in Mexico to help track human swine flu levels. Experimental Flu Trends for Mexico is, as you might have guessed, very experimental. But the system has detected increases in flu-related searches in Mexico City (Distrito Federal) and a few other Mexican states in recent days, beginning early in the week of April 19-25.
In the United States, we were able to validate our estimates using data from a surveillance system managed by the U.S. Centers for Disease Control and Prevention (CDC). We have not verified our data for Mexico in the same manner, but we've seen that Google users in Mexico (and around the world) also search for many flu-related topics when they have flu-like symptoms. Given the tremendous recent attention to swine flu, our model tries to filter out search queries that are more likely associated with topical searches rather than searches by those who may be experiencing symptoms.
While we would prefer to validate this data and improve its accuracy, we decided to release an early version today so that it might help public health officials and concerned individuals get an up-to-date picture of the ongoing swine flu outbreak. As with our existing Flu Trends system, estimates are provided across many of Mexico's states and updated every day. Our current estimates of flu activity in the U.S. are still generally low as would be expected given the relatively low confirmed swine flu case count. However, we'll be keeping an eye on the data to look for any spike in activity.
We're keenly aware of the trust our users place in us and our responsibility to protect their privacy. Experimental Flu Trends for Mexico -- like Google Flu Trends -- cannot be used to identify individual users. The patterns we observe are only meaningful across large populations of Google searchers. We hope that this experimental release provides useful information.
For updates on swine flu and information on how to stay healthy during a disease outbreak, visit the CDC's swine flu site.