Last year, Google released a report which showed that flu-related search terms are good indicators of flu activity. Google Flu Trends uses information about the popularity of some searches in the US to estimate flu activity almost in real-time.
The experiment has been expanded to the searches from Mexico, the country that has the largest number of reported cases of swine flu. "Unlike Google Flu Trends for U.S., Experimental Flu Trends for Mexico was not built using historical data on flu symptoms. This means the models have not been checked against actual historic flu data from Mexico and thus the estimates you see for Mexico are unverified. The models for Mexico are based on aggregated search queries likely to be associated with influenza-like illness."
Google's search data showed that flu-related queries started to become more frequent this month. "Last week, at the request of the Centers for Disease Control, Google took a retroactive look at its search data from Mexico. And there the team found a pre-media bump in telltale flu-related search terms (you know, "influenza + phlegm + coughing") that was inconsistent with standard, seasonal flu trends," reports Wired. "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," informs Google's blog.
A map that lists the latest cases of swine flu is available at Google Maps.