Nov. 6 (Bloomberg) -- Google Flu Trends, the influenza- monitoring service of Google Inc.’s philanthropic arm, tracked swine flu almost as well as the surveillance systems maintained by health-care workers, scientists in New Zealand found.

Flu Trends yielded results “fairly congruent with actual surveillance systems,” the researchers found. The free, online program would be especially useful in tracking cases where data are lacking or normal surveillance systems are disrupted, they said in a study yesterday in the journal Eurosurveillance.

The new H1N1 virus, which sparked the first influenza pandemic in 41 years, is bolstering demand for information on flu patterns as authorities prepare for a surge in hospitalizations. The Google program, unveiled a year ago, uses Internet-search queries to track the spread of the flu, aiming to identify outbreaks more quickly than systems that rely on medical data.

“We are still learning about it, but it looks like it could be a reasonable system to have as a backup,” said Nick Wilson, a public health physician at the University of Otago in Wellington who led the study. “It performed a bit better than I expected.”

The researchers compared Flu Trends with three existing flu-monitoring systems, including a sentinel surveillance system based on a network of general practitioners, from March 29 to Oct. 4. Flu infections typically surge during winter, which runs from June 1 to Aug. 31 in New Zealand.

They found that the Google program and GP surveillance data both showed increases in weekly rates of influenza-like illness from May 3. Flu Trends showed rates peaked in the week starting July 5, one week earlier than indicated by the GP data, and remained at higher levels from mid August through early October.

No Advance Warning

The week in which flu rates were the highest according to Google coincided with the peak in hospitalizations and admissions to intensive care units in New Zealand, the authors said. Flu Trends, though, wouldn’t have provided any advance warning of flu-like illness compared with the weekly reporting from computerized data from doctors’ offices.

The online program could play an important role if the normal surveillance systems were disrupted, such as by a particularly severe pandemic where health systems are overburdened, or when people with mild illness are discouraged from visiting doctors, the researchers said.

“Google Flu Trends should therefore continue to be closely studied,” they said.

Google.org, the philanthropic arm of the owner of the world’s largest search engine, says it found a relationship between people searching for flu-related topics and those with symptoms.

Flu Predictor

“We compared our query counts with traditional flu surveillance systems and found that many search queries tend to be popular exactly when flu season is happening,” Google.org said on its Web site. “By counting how often we see these search queries, we can estimate how much flu is circulating in different countries and regions around the world.”

The Mountain View, California-based organization said Flu Trends has been expanded to 20 countries and 38 languages.

“Since it is a free system, I would hope that it gets expanded to cover all countries in the world,” Wilson said in an e-mailed response to questions. “This means we in the public health community are not so dependent on relying on governments to report on the situation, especially autocratic governments that might try to be less than fully transparent.”

To contact the reporter on this story: Jason Gale in Singapore at j.gale@bloomberg.net

Last Updated: November 6, 2009 03:14 EST