Google just launched an updated version of Google Flu Trends, a service that predicts flu trends by tracking flu-related queries on the company's search engine. Until now, Google only showed aggregate data for states in the United States. Starting today, Flu Trends will show data down to the city level for 121 cities. As Google notes in today's announcement, this update was timed to coincide with National Influenza Vaccination Week.

Google also offers Flu Trends data on a country level for Mexico, Australia, New Zealand and most of Western Europe. Data on Flu Trends is updated daily.

By tracking flu-related queries, Google has already proven to be able to accurately predict the flu levels on a state and country level. It looks like Google now feels like its algorithms are accurate enough to predict influenza trends on a more granular level. Until Google is able to validate this data, however, the company is labeling the city level estimates as "experimental."

Google and Google.org - Google's non profit foundation - sponsor a number of influenza-related projects. Google, for example, now offers a vaccine-finding map and the company is working with the Public Library of Science (PLoS) to to give give scientists a place to collaborate and share research on influenza research on Google Knol.