Using a new tracking tool, search engine giant Google said on Wednesday it saw a spike in searches for information about flu among people in Mexico last week even before news of the outbreak became widely known.

Google said it has put together a flu trends tracking system for Mexico based on the U.S. Google Flu tool launched last fall that is used by U.S. Centers for Disease Control and Prevention to figure out where influenza is heating up.

It is based on Google's observation that people who are sick with flu tend to search for the same types of information on the Internet, and these searches can be used to predict where an outbreak may be occurring.

We have seen evidence in Mexico that Google users also search flu-related topics when they are experiencing flu-related symptoms, Jeremy Ginsberg, lead engineer for Flu Trends at Google, said in a telephone briefing.

Studies show that between 35 and 40 percent of all visits to the Internet are started by people looking for health information.

Ginsberg said the Mexican data have not been cross-checked with years of data on actual flu cases in Mexico like the U.S. flu tracker has, so the data may not be reliable.

But he said the company is optimistic that the system, which generates maps based on peaks in flu-related searches, may reflect actual flu activity.

We did see a small increase in many parts of Mexico before major news coverage began last week, he said.

Ginsberg said people search for different things when they are sick -- like the word thermometer -- than they do when they are looking for news about flu outbreaks.

Ginsberg said the group has also seen a spike in U.S.-related flu searches that correspond with increases in U.S. cases being reported.

He said the hope is that the tool might offer one more way to predict hot spots in an outbreak as they happen.

If it spreads quickly, it may give public health officials the chance to respond quickly, he said.

Google's flu tool for Mexico can be found at

(Editing by Maggie Fox)