Google Uses Searches to Track Flu’s Spread
SAN FRANCISCO — What if Google knew before anyone else that a fast-spreading flu outbreak was putting you at heightened risk of getting sick? And what if it could alert you, your doctor and your local public health officials before the muscle aches and chills kicked in?
That, in essence, is the promise of Google Flu Trends, a new Web tool that Google.org, the company’s philanthropic unit, unveiled on Tuesday, just as flu season was getting under way in the United States.
Google Flu Trends is based on the simple idea that people who are feeling sick will probably turn to the Web for information, typing things like “flu symptoms” or “muscle aches” into Google. The service tracks such queries and charts their ebb and flow, broken down by regions and states.
Early tests suggest that the service may be able to detect regional outbreaks of the flu a week to 10 days before they are reported by the Centers for Disease Control and Prevention. Some public health experts say that could help accelerate the response of doctors, hospitals and public health officials to a nasty flu season, reducing the spread of the disease and, potentially, saving lives.
It could also offer a dose of comfort to stricken individuals in knowing that a bug is going around.
“This could conceivably provide as early a warning of an outbreak as any system,” said Lyn Finelli, lead for surveillance at the influenza division of the C.D.C. Ms. Finelli noted that people often search the Internet for medical information before they call their doctor.
“The earlier the warning, the earlier prevention and control measures can be put in place, and this could prevent cases of influenza,” Ms. Finelli said. Between 5 and 20 percent of the nation’s population contracts the flu each year, Ms. Finelli said, leading to an average of roughly 36,000 deaths.
Google Flu Trends (www.google.org/flutrends) is the latest indication that the words typed into search engines like Google can be used to track the collective interests and concerns of millions of people, and even to forecast the future.
“This is an example where Google can use the incredible systems that we have to come up with an interesting, predictive result,” said Eric E. Schmidt, Google’s chief executive. “From a technological perspective, it is the beginning.”
For now the service covers only the United States, but Google is hoping to eventually use the same technique to help track influenza and other diseases worldwide.
The premise behind Google Flu Trends has been validated by an unrelated study indicating that the data collected by Yahoo, Google’s main rival in Internet search, can also help with early detection of the flu.
“In theory, we could use this stream of information to learn about other disease trends as well,” said Philip M. Polgreen, assistant professor of medicine and epidemiology at the University of Iowa and a co-author of the study based on Yahoo’s data.
Still, some public health officials note that many health departments already use other techniques, like gathering data from visits to emergency rooms, to keep daily tabs on disease trends in their own communities.
“We don’t have any evidence that this is more timely than our emergency room data,” said Farzad Mostashari, assistant commissioner of the New York City Department of Health and Mental Hygiene.
If Google provided health officials with details of the inner workings of the system so that it could be validated scientifically, the data could serve as an additional way to detect influenza that was free and might prove valuable, said Mr. Mostashari, who is also chairman of the International Society for Disease Surveillance.
A paper on the methodology behind Flu Trends is expected to be published in a future issue of the journal Nature.
Researchers have long said that the data sprinkled throughout the Web amounts to a form of “collective intelligence” that could be used to make predictions. Commercial Web sites mine this information to predict airfares or home prices.
But the data collected by search engines is particularly powerful, because the keywords and phrases that people type into search engines represent their most immediate intentions. People may search for “Kauai hotel” when they are planning a vacation and for “foreclosure” when they get in trouble with their mortgage. Those queries express the world’s collective desires and needs, its wants and likes.
Internal research at Yahoo suggests that increases in searches for certain terms can help forecast what technology products will be hits, for instance. Yahoo itself has begun using search traffic to help it decide what material to feature on its home page. It analyzes what its users are interested in and then programs its Web site accordingly.
Two years ago, Google began opening its search data trove through Google Trends, a tool that allows anyone to track the relative popularity of search terms. Google also offers more sophisticated search traffic tools that marketers can use to fine-tune advertising campaigns. And internally it has tested the use of search data to reach conclusions about economic, marketing and entertainment trends. It found both promises and limitations.
“This works remarkably well, but tends to miss ‘turning points,’ times when the data changes direction,” said Hal Varian, Google’s chief economist.
Prabhakar Raghavan, who is in charge of Yahoo Labs and the company’s search strategy, also said search data could be immensely valuable for forecasters and scientists, but concerns about privacy had generally stopped the company from sharing it with outside academics.
Google Flu Trends gets around privacy pitfalls by relying only on aggregated data that cannot be used to identify individual searchers. To develop the service, Google’s engineers devised a basket of keywords and phrases related to the flu, including thermometer, flu symptoms, muscle aches, chest congestion and many others. Google then dug into its database, extracted five years of data on those queries and mapped the data onto the C.D.C.’s reports of “influenzalike illness,” which the agency compiles based on data from labs, health care providers, death certificates and other sources. Google found an almost perfect correlation between its data and the C.D.C. reports.
“We know it matches very, very well in the way flu developed in the last year,” said Larry Brilliant, executive director of Google.org. Ms. Finelli of the C.D.C. and Mr. Brilliant both cautioned that the data needed to be monitored to ensure that the correlation with flu activity remained valid.
Other people have tried to use information collected from Internet users for public health purposes. A Web site called whoissick.org, for instance, invites people to report about what ails them and superimposes the results on a map. But the site has received little traffic, so its usefulness is limited.
HealthMap, a project affiliated with Children’s Hospital Boston and Harvard Medical School, scours the Web for news articles, blog posts and electronic newsletters to create a map that tracks emerging infectious diseases around the world. It is backed by Google.org, which counts the detection and prevention of diseases as one of its main philanthropic objectives.
But Google Flu Trends appears to be the first public project that uses the powerful database of a search engine to track the emergence of a disease.“This seems like a really clever way of using data that is created unintentionally by the users of Google to see patterns in the world that would otherwise be invisible,” said Thomas Malone, a professor at the M.I.T. Sloan School of Management. “I think we are just scratching the surface of what’s possible with collective intelligence.”