In New Tools to Combat Epidemics, the Key Is Context Not long ago, Google Flu seemed like magic - a smart, cheap way to sift digital data for the public good. But Google Flu, which tries to track flu outbreaks faster than the government, has shown its limitations. Not only did it grossly overestimate the flu this year, but its methods did little to track new, deadly diseases that could emerge anywhere, in places as random as a mass religious gathering on the banks of the Ganges or a poultry market in Shanghai. Now a new project called BioMosaic is building a more comprehensive picture of foreign-borne disease threats in the United States, by merging three separate data tools into a single app for guiding decisions at the time of an outbreak. "The best way to get these big-picture perspectives is to look at multiple layers of data," said Dr. Marty Cetron, the director of the division of global migration and quarantine at the federal Centers for Disease Control and Prevention, who had the idea for the project. By combining airline records, disease reports and demographic data, BioMosaic lets public health officials visualize health risks through a Web site and an iPad app. They can then deploy preventive measures to individual cities, counties or even hospitals to help thwart a larger crisis. For example, after the 2010 earthquake in Haiti and subsequent cholera epidemic, BioMosaic showed where clusters of the 500,000 to 800,000 Haitian-born residents in the United States were most likely to live, along with air and sea travel routes to and from Haiti, to pinpoint where anti-cholera measures in the United States would be most useful. "It really helps you get right to the heart of the matter: that concept that a global event in Haiti becomes a local event in five counties in Florida and five counties in New York," Dr. Cetron said. When you see it, you get these aha! moments of appreciation. One of the doctors in the field who can benefit from these types of insights is Dr. Kamran Khan, an infectious disease specialist and researcher at St. Michael's Hospital in Toronto. Dr. Khan, who said he had a "bad habit of being around emerging diseases," has worked on the front lines of the 1999 West Nile virus outbreak and the H1N1 pandemic of 2009. But the event that hit closest to home was when his own hospital was affected by a deadly outbreak of severe acute respiratory syndrome, or SARS, which hit Toronto in 2003. That spring, the city had received an infected passenger from Hong Kong who passed SARS to family members, activating quarantine measures across the city. Despite those efforts, 44 people eventually died across Canada, including two nurses and a doctor. "No one wanted to come near you," he said. You quickly became an outcast in society. Once the outbreak was over, studies showed that cities like Toronto, with direct flights from Hong Kong, were 25 times as likely to record SARS cases as cities that could be reached only through a connecting flight. Cities that were two flight connections away from Hong Kong never observed a single case. "It was this moment of recognizing the world is extremely interconnected," Dr. Khan said. That was the impetus for him to start digging for data on human movements around the globe in his project called BioDiaspora, from international air travel to large mass gatherings like the hajj, the Olympics or the World Cup. Dr. Khan spent years negotiating with air traffic organizations, governments and airlines to amass a database of human movement around the globe, encompassing 4,000 airports and 30 million flights a year, carrying 2.5 billion passengers. With that information, he can better predict the likelihood of where a single case of bird flu in Asia, for instance, might eventually surface on other continents. It is powerful data, but made even more so when placed in BioMosaic alongside a mapping tool that tracks on-the-ground disease reports. That part of the puzzle is HealthMap, which was created by a team at Boston Children's Hospital under the direction of John Brownstein, a professor at Harvard Medical School. His staff monitors everything from Arabic news reports on cholera to a local television story about a rabid bat in Ohio. Each report is tagged and placed on a publicly available map that offers a global snapshot of infectious disease. HealthMap employs translators who read articles and social media mentions in 15 different languages. Recently they found the medical record of a patient with the avian flu virus H7N9 on the Chinese social media site Weibo. "It was the most striking thing," Dr. Brownstein said. If you think about the difference between that and SARS, we're in a whole new world now. While BioMosaic is helping public health officials see rising threats more clearly, the holy grail for this kind of technology would be the ability to actually to predict an outbreak before it begins, Dr. Brownstein said. But still there are limits. "Information will only get us so far," said Dr. Khan, whose personal experience has made him aware that equally pernicious forces, such as politics, nationalism, strained resources and fear, can, in a crisis, override even the best data tools.