A lot of ailing Americans enter phrases like "flu symptoms" into Google and other search engines before they call their doctors. That simple act has given rise to a new early warning system for fast-spreading flu outbreaks, called Google Flu Trends. Tests of the new Web tool from Google.org, the company's philanthropic unit, suggest that it may be able to detect regional outbreaks of the flu a week to 10 days before they are reported by the Centers for Disease Control and Prevention. The CDC reports are slower because they rely on data collected and compiled from thousands of healthcare providers, labs, and other sources. Some public health experts say the Google data 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.