Officials at ProMED-mail, another disease-tracking site with 50,000 subscribers, applaud the effort.

"It's very nice getting to see these things geographically," says ProMED editor Larry Madoff, an associate professor of medicine at Harvard Medical School.

He predicts that information from sources such as pharmacy sales of certain medications, and even indirect indicators like the stock market, could also inform disease tracking in powerful ways.

"At this point, I think we are just scratching the surface about what's out there," Madoff says.