Hulth and Rydevik BMC Public Health 2011, 11:252 http://www.biomedcentral.com/1471-2458/11/252 first comparison between data from the general purpose search engine Google and data collected from the medi- cal web site SMI collaborates with, by investigating the amount of epidemiologically useful information that can be obtained from the two sources for two different queries. In 2006, Eysenbach showed a correlation between clicks on a keyword triggered link on Google and Cana- dian influenza activity [1]. Queries submitted to the Google search engine, which have shown a correlation with historical influenza data, are used to monitor influ- enza in a number of countries in an application called Google flu trends [2-4]. Influenza queries from another general purpose search engine – Yahoo – have also been shown to correlate with official influenza data [5]. Listeriosis is another infectious disease that has been retrospectively analyzed from Yahoo search queries [6]. Statistical models for estimating the influenza burden have been developed on queries submitted to the search engine on a Swedish medical web site [7]. Additionally, a system based on web logs is naturally not restricted to infectious diseases. Cooper et al have studied the corre- lation between Yahoo queries and common cancer forms in the US [8]. However, infectious diseases are the focus of the presented research as it is to be Page 2 of 8 beneficial for the infectious disease control and preven- tion in Sweden. Methods Query data The search queries, which are the core of the GET WELL application, originate from the search engine on the medical web site Vårdguiden.se [9]. This web site is owned by the Stockholm County Council. Stockholm County covers roughly one fifth of the 9.3 million inha- bitants in Sweden. Vårdguiden estimates that 55 per cent of the visitors live in Stockholm County, while the rest live in other parts of the country (or the world) [10]. In November 2009, the web site had 2.5 million visitors (a number which was probably increased due to the influenza pandemic) [11]. All queries submitted to the search engine on Vårdguiden are logged, and date and time are included in each log entry. No information that could potentially reveal the identity of a web site visitor is stored, nor any information that can tie a visi- tor to a geographical location. The application and its implementation The GET WELL application is available on the SMI intranet since January 2010. In Figure 1, a flow chart of Figure 1 Flow chart. A flow chart of GET WELL.