I have said it before, I will say it again: I love Google. The health care professional in me is THRILLED at the company’s newest invention: Google Flu Trends.

Combating the flu by deploying the Web

What if Google knew before anyone else that a 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 Web tool that Google.org, the company’s philanthropic unit, announced Tuesday, just as the flu season was starting.

Google Flu Trends is based on the idea that people feeling sick are likely to turn to the Web for information, searching on Google for phrases like “flu symptoms” or “muscle aches.” Google Flu Trends tracks such queries and charts their ebb and flow, broken down by regions across the United States.

Google.org said this first version of Google Flu Trends “is just a start” and it hoped to “explore other countries, languages, and diseases in the future.”

Early tests suggest that the service might be able to detect regional outbreaks of the flu between a week and 10 days before they are reported by the U.S. Centers for Disease Control.

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 of the influenza division of the Centers for Disease Control and Prevention.

“The earlier the warning, the earlier prevention and control measures can be put in place, and this could prevent cases of influenza,” Finelli said.

Between 5 percent and 20 percent of the population of the United States contracts the flu each year, Finelli said, leading to an average of 36,000 deaths.

Google Flu Trends 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 Schmidt, the Google chief executive. “From a technological perspective, it is the beginning.”

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. The study, by the University of Iowa College of Medicine, suggested that the technique could be applied to the surveillance of other diseases in the future.

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  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.

If Google could provide health officials with more details of how its system works, the data could be an additional way to detect influenza that may prove quite valuable, said Mostashari, who is also chairman of the International Society for Disease Surveillance.

Researchers have long said that the data sprinkled throughout the Web could be used to make predictions. There are commercial Web sites that mine that information to predict airfares and 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.

Research at Yahoo suggests that increases in searches for certain terms can help predict events. Yahoo has begun using search traffic to make decisions about ranking news articles on its site.

Two years ago, Google began opening up its search data through Google Trends, a tool that allows anyone to track the popularity of search terms. It also offers more sophisticated search traffic tools that marketers can use to test advertising campaigns.

Google Flu Trends is based on the same idea. Google’s engineers created 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 Centers for Disease Control and Prevention’s reports of “influenza-like illness,” which the agency collects from laboratories, health care providers and other sources. Google found an almost perfect correlation between its data and the center’s 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.

Finelli and Brilliant cautioned that the data needed to be monitored to ensure that the correlation with flu trends remained valid.

Other projects have tried to use information collected from Internet users for public health purposes. A Web site called whoissick.org, for instance, invites people to post information 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 the Children’s Hospital in Boston, 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 disease as one of its main goals.

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. The approach has the potential to detect other diseases.

“In theory, we could use this stream of information to learn about other disease trends as well,” said Philip Polgreen, assistant professor of medicine and epidemiology at the University of Iowa. Polgreen is a co-author of the study that used Yahoo’s search data to detect influenza, which will be published next month.