Want to know how bad the flu is in your state? Ask Google.

The all-knowing search engine has a new tool, Google Flu Trends, that estimates U.S. flu activity up to two weeks earlier than government disease trackers.

The gadget compiles the info by aggregating search queries for the virus geographically. It then spits out daily estimates of where outbreaks are likely. (The U.S. Centers for Disease Control and Prevention (CDC) provides weekly updates based on reports on flu activity from doctors around the country). "We have found a close relationship between how many people search for flu-related topics and how many people actually have flu symptoms," Google said yesterday in an explanation of the tool on its Web site. "Of course, not every person who searches for 'flu' is actually sick, but a pattern emerges when all the flu-related search queries from each state and region are added together."

When Google compared an early version of its Flu Trends last year with the CDC's own records, it accurately estimated the extent of disease up to two weeks more quickly in each of the agency's nine surveillance areas, Google said. "By making our flu estimates available each day, Google Flu Trends may provide an early-warning system for outbreaks of influenza," Google said.

Lyn Finelli, head of the CDC's flu surveillance division, agreed. "This could conceivably provide as early a warning of an outbreak as any system," Finelli told the New York Times, noting that many people often search online for flu symptoms before calling their doctor. "The earlier the warning," she added, "the earlier prevention and control measures can be put in place, and this could prevent cases of influenza."

Some 200,000 people are hospitalized with the flu and 36,000 die of it in the U.S. each year, according to the CDC. But skeptics say the gadget isn't better than collecting information on flu-related visits to local emergency rooms. “We don’t have any evidence that this is more timely than our emergency room data,” Farzad Mostashari, assistant commissioner of the New York City Department of Health and Mental Hygiene, told the Times.

Right now, Google Flu Trends is only tracking the virus in the U.S., according to the newspaper, though it hopes to eventually expand to other countries and diseases. But will there be a digital divide in the gadget's success, which depends on people's use of the Internet? Authorities are having a hard enough time tracking a new spike in cholera in the Democratic Republic of Congo; are refugees there going to be searching Google for symptoms?

Image by iStockphoto/Joseph Jean Rolland Dubé