Google says it is able to track swine flu levels in Mexico by looking at how many people search terms such as "aches and chills."

Google has published a new feature called Experimental Flu Trends for Mexico, but is cautioning it hasn't yet been able to verify the data.

An expansion to their existing flu trends tool for the U.S., Google says its data showed a small increase in many parts of Mexico before swine flu hit the news last week.

Jeremy Ginsberg, the lead engineer for Flu Trends, says his team is looking at the potential to use the approach in a number of other countries.

Ginsberg says Flu Trends is able to distinguish people just searching for information on swine flu from people who think they may have the flu.

Some of the search terms they look for include stomach problems, aches and chills and searches on where to buy a thermometer.

"For Flu Trends US we found a set of terms that, going back a number of years in different places across the U.S., really matched," Ginsberg said in a conference call Wednesday.

"The popularity of these terms increased exactly when official surveillance data said more people were experiencing flu-like symptoms."