Flu Trends uses aggregated Google Search data to estimate current flu location and activity around the world in near real-time
Each week, millions of users around the world search for health information online. Google has found a close relationship between how many people search for flu-related topics and how many people actually have flu symptoms. Google Flu Trends compared its query counts with traditional flu surveillance systems and found that many search queries tend to be popular exactly when and where the flu season is on. By counting the frequency of these search queries, one can estimate how much flu is circulating in which country and regions around the world.
How the location matters?
Google Flu Trends uses IP address information from the server logs to make a best guess about where the location of the queries as per country, region and states. For epidemiologists, this is an exciting development, because early detection of a disease outbreak can reduce the number of people affected. The up-to-date influenza estimates could enable public health officials and health professionals to better respond to seasonal epidemics and pandemics.
Google Flu Trends compares the estimates based on search data against a historic baseline level of flu activity for that area. Depending on whether the current estimate is higher or lower than the baseline, the system reports the general activity level as Minimal, Low, Moderate, High, or Intense.
Google Web search queries can be used to accurately estimate influenza-like illness (ILI) percentages in each of the nine public health regions of the United States. If a region experiences an early, sharp increase in ILI physician visits, it may be possible to focus additional resources on that region to identify the etiology of the outbreak, providing extra vaccine capacity or raising local media awareness as necessary.
How accurate and up-to-date is this?
Most health agencies focus on a single country or region and only update their estimates once per week. However, on Google Flu Trends, estimates for the current week are updated daily as new search query data is collected. The graphs show historical query-based flu estimates for different countries and regions compared against official influenza surveillance data and are found to be mostly in line with traditional surveillance data collected by health agencies.
For countries with experimental Flu Trends, Google found aggregated flu-related queries which produced a seasonal curve that suggested actual flu activity. Generally, these estimates have not been compared with official influenza surveillance data. The experimental estimates are available for download from each Experimental Flu Trends country page.
Since Google Flu Trends models are validated using historic flu surveillance data, in case of a pandemic, when a new flu virus causes the same symptoms as seasonal flu, the graphs should detect if overall flu rates are significantly increasing. In the event that a pandemic-causing strain of influenza emerges, accurate and early detection of ILI percentages may enable public health officials to mount a more effective early response. Currently, Google provides estimates for more than 25 countries and anyone connected to the Internet can access this.