Google has expanded its Flu Trends tracking tool to include 16 more countries.

The company, which launched the free tool in the US in November 2008, had already made the tool available in Australia, New Zealand and Mexico.

The latest expansion means it is now tracking the spread of influenza across Austria, Belgium, Bulgaria, Canada, France, Germany, Hungary, Japan, Netherlands, Norway, Poland, Russia, Spain, Sweden, Switzerland and the Ukraine.

The tool counts the number of flu-related queries typed into the Google search engine and predicts influenza outbreaks by analysing flu patterns in each region.

Information also comes from various sources, such as the European Influenza Surveillance Network of the European Centre for Disease Prevention and Control.

According to Google engineers Matt Mohebbi and Dan Vanderkam, last season the flu spread estimates made using Google search terms closely mirrored those figures later released by US health officials.

They said: “By tracking the popularity of certain Google search queries, we are able to estimate the level of flu in real-time.

“While some traditional flu surveillance systems may take days or weeks to collect and release data, Google search queries can be counted immediately.”

Google also filters out certain terms that may be popular searches because people have heard about them in the news such as “swine flu” rather than because they are showing flu-like symptoms.

The expansion comes shortly after Microsoft launched its new website, “H1N1 Response Centre,” which provides people with up to date information and advice on flu and allows them to monitor symptoms and get advice using a self-service tool.

Links: Google Flu Trends

Microsoft H1N1 Response Centre