We built Google Flu Trends as a complementary data source to the surveillance systems run by the CDC.

FORBES: How Accurate Is Google Flu Trends?

Google Flu Trends was launched to the public in November 2008 as a new way to track flu activity.

CNN: Flu season picking up speed, tracking indicates

Health professionals around the world already use online tools, such as Google Flu Trends, Health Map or Global Public Health Intelligence Network to track the spread of infectious diseases.

BBC: Can crowdsourcing beat the flu?

The Centers for Disease Control and Prevention (CDC), which tracks flu cases reported from local health departments, typically picks up on cases a couple of weeks after Google Flu Trends.

CNN: Flu season picking up speed, tracking indicates

During last year's flu season, Google Flu Trends picked up a significant rise in such search terms on January 28, 2008, and two weeks later the CDC saw a rise in cases reported from local health departments.

CNN: Flu season picking up speed, tracking indicates

Google's Flu Trends looks at search terms to create real-time estimates of where the flu is flaring up.

CNN: Tracking the flu with technology and Twitter

Google's Flu Trends, which monitors millions of queries submitted to the giant search engine for the occurrence of flu-related keywords, is at best contemporaneous with an outbreak.

ECONOMIST: Epidemiology: Infectious personalities | The