Searching for the flu

ATLANTA, GA.; November 11, 2008

A collaboration between Google and the U.S. Centers for Disease Control and Prevention in Atlanta has yielded an online tool that may help people know about flu outbreaks even more quickly than existing surveillance methods.

The new tool, called Google Flu Trends<\a>, will monitor search trends to see abnormally large numbers of searches for the flu and related terms. It will then publish a map of affected areas in its new service.

Google says its new system will be able to detect influenza outbreaks up to two weeks faster than the traditional surveillance systems in use.

"As with any communicable disease, early detection is key for health professionals to react quickly," said Jeremy Ginsberg, the lead engineer who developed the new site.

"With online search queries, what we see is millions of people who are interested in searching online for information about health. And with winter approaching, more people will be curious about flu, because we are entering the flu season."

A paper accompanying the launch of the site was accepted by the journal Nature, with the editor-in-chief Philip Campbell praising the "exceptional public-health implications of this paper."

The journal is of allowing the paper to be discussed with the public before it is published.

But while researchers in the field call the new system interesting and novel, they are not ready to get behind the new site yet.

"I think the way to tell, obviously, is to compare it with actual surveillance data, which they should be able to pick up locally," said Stephen Morse, an epidemiologist at Columbia University's Mailman School of Public Health. "Whether searching for the flu is meaningful or not can only be compared with another gold-standard method."

Morse said the system is open to a few problems.

"I think the approach sounds like a reasonable one, but I can think of several reasons why people might want to search for information on the flu," he said.

For example, Morse noted, as a flu researcher, he searches for flu information constantly, despite not being ill. More prevalent problems could accompany an increase in flu-related search terms because of a media report about the flu or, at this point, the threat of avian influenza.

Others have similar concerns.

"It's certainly intriguing and outside-of-the-box," said Dr. Lisa Jackson, an infectious disease specialist with the Group Health Center for Health Studies in Seattle. "The difficulty is that the term flu is not just used for influenza. A lot of people think of flu as a gastrointestinal issue."

She cited the rhinovirus, which causes stomach flu, along with the norovirus and rhinovirus, which cause the common cold -- which many mistake for flu -- as possible confounders of Google's new system.

"I think a big problem is that the term flu is used for lots of different things, so right away you have an issue with that," Jackson said. "I'm not sure how well [Google Flu Trends] will translate into helping us identify areas of influenza activity."

In response to concerns like this, Ginsberg said that in researching the new site, the data that is gathered from search engine queries is compared against past search trends and physician data. In the past, the trends in searching for flu have lined up well with actual outbreaks.

"What we have done is actually looked at four or five years of all of the data collected by the CDC's network of physicians. ... We compared that to the aggregated search queries on the flu over the past five years. We realized that the correlation tends to be very, very tight." It remains unclear, however, how the information will be affected by the possibility of manipulation on the Internet by people hoping to alter results.

Still, while they are waiting to see the results of the new system, researchers say that unconventional methods like this have had some success in the past.

Jackson cited an outbreak of diarrhea several years ago in Milwaukee that was caused by a faulty septic system. She noted that the outbreak was caught because pharmacists in the area noticed that the diarrhea drug Imodium and toilet paper were flying off the shelves.

Morse noted that another Web site with a similar concept to Google Flu Trends, called Who is Sick?, asks sick individuals to describe their symptoms. They can then observe if others in their area have similar illnesses.

Morse also indicated that better surveillance is certainly needed for figuring out where outbreaks of flu occur.

"Determining when a flu outbreak begins is difficult because there's a tendency not to report it," he said.

"Flu is underreported. People don't tend to go to hospitals or physicians unless they think they are very sick. What you're seeing, usually, when you actually get reports of flu outbreak, is those who are sick enough."

Morse said novel methods that observe human behavior to make predictions about disease outbreaks greatly aid the fight against influenza.

"I think we need a lot of ideas like this," he said.