What do hemorrhoids, One Direction, and Big Bird all have in common? According to Google Trends, they were among 2012's most popular Internet search terms with the highest sustained traffic. What do hemorrhoids, One Direction, and Big Bird all have in common? According to Google Trends, they were among 2012's most popular Internet search terms with the highest sustained traffic. Google Trends (www.google.com/trends/) is a Web-based tool available to all Internet users that estimates the search volume of a specific term or topic relative to the total number of Web searches over a period of time. Users can create graphs of search volume, updated daily, based on data from specific countries or worldwide. One potential application of this tremendous volume of Web searches is for better insights into the health information sought by patients around the world.■Search engine surveillance tools like Google Trends can help identify public health issues as they emerge.■While more research is needed on the value of search engine data, it is likely to play a role in the future of public health. ■Search engine surveillance tools like Google Trends can help identify public health issues as they emerge.■While more research is needed on the value of search engine data, it is likely to play a role in the future of public health. Syndromic surveillance has recently emerged as a means to detect outbreaks through symptom monitoring, even before confirmed diagnoses are available. Adequate surveillance usually requires careful coordination of several teams and agencies to communicate threats, organize responses, and interface with multiple stakeholders, including the public. This requires time, manpower, financial resources, and a stable infrastructure for effective execution. Public health surveillance tools can provide real-time information to monitor emerging threats. These surveillance tools can help prevent major outbreaks by tracking diseases, monitoring their spread, and aiding in planning for rapid and effective response. As Internet utilization continues to grow around the world, the search terms used in a certain geographic area can provide potential insights into emerging health trends. Using the Internet, individuals can search from home for answers about medical questions that may render them weak and unable to travel, or that may carry heavy social stigma or embarrassment. Understanding health trends can provide clues into the experience of a population and enable local governments and response teams to counter any threats in a timely and effective manner. ■Global Public Health Intelligence Network (Public Health Agency of Canada): www.phac-aspc.gc.ca/gphin/■HealthMap (Boston Children's Hospital): www.healthmap.org■Program for Monitoring Emerging Diseases (International Society for Infectious Diseases): www.promedmail.org In 2008, Canada experienced an outbreak of listeriosis resulting from deli meat contaminated with Listeria bacteria. Although the public health declaration occurred in August, search-term surveillance revealed a rise in searches for "listeriorisis" as early as July.1.Wilson K. Brownstein J.S. Early detection of disease outbreaks using the Internet.CMAJ. 2009; 180: 829-831Crossref PubMed Scopus (194) Google Scholar This case is just one example of the potential role of search-term surveillance. Tools like Google Trends can provide nearly real-time data that may allow researchers and health officials to identify epidemics as they emerge, particularly in developing countries that lack robust public health infrastructure and financial resources for surveillance.2.Carneiro H.A. Mylonakis E. Google trends: a Web-based tool for real-time surveillance of disease outbreaks.Clin Infect Dis. 2009; 49: 1557-1564Crossref PubMed Scopus (454) Google Scholar Recently, public health groups have used Google Trends as a surveillance tool for early identification of outbreaks and potential health threats. In 2008, Google launched Flu Trends (www.google.org/flutrends/) to specifically track and predict real-time flu outbreaks in countries around the world, including the United States. This tool monitors search queries on Google to identify the presence of influenza symptoms, categorizing flu activity as minimal, low, moderate, high, or intense compared with past flu activity. Compared with retrospective surveillance data from CDC, Google Flu Trends accurately detected emerging cases of influenza almost 2 weeks prior to the agency's published reports.2.Carneiro H.A. Mylonakis E. Google trends: a Web-based tool for real-time surveillance of disease outbreaks.Clin Infect Dis. 2009; 49: 1557-1564Crossref PubMed Scopus (454) Google Scholar Though search engine surveillance tools seem promising, this technology is still developing and is not without its limitations. Google Trends data do not use standardized search criteria and can be overestimated, as reflected in its estimated 2013 influenza outbreak numbers, which were nearly double those calculated by CDC. Actual raw data will be needed in order to carry out more robust and meaningful analysis and comparison with other surveillance data, such as those from CDC. Nonetheless, Google Trends, in addition to other search engine surveillance tools, may have an increasingly important role in the early detection of outbreaks and timely communication with the public.