The ubiquitous Fitbit, a wearable device that can measure everything from the number of steps you take each day to your heart rate and sleep time, can help users manage their weight and overall health. Researchers now believe it can have an even larger purpose: providing an early warning system for influenza outbreaks.

Each year, around 650,000 people worldwide die from the flu, and public health officials have long struggled for ways to get in front of potential outbreaks. They have tried tools such as Google Flu Trends to capture real-time crowd-sourced health data that could indicate populations where the flu is gaining a foothold, a method known as nowcasting. But so far, they have had limited success.

Teams at Scripps Research in California focused on a Fitbit’s ability to identify abnormal fluctuations in a person’s resting heart rate and activity patterns, often indicators of an acute infection.

They got data from 200,000 unidentified Fitbit users from March 2016 to March 2018 in five states: California, Texas, New York, Illinois and Pennsylvania. They then correlated the data with flu reports from those states from the Centers for Disease Control and Prevention. They found the weeks when the Fitbit users had elevated heart rates and more sleep time corresponded to periods when flu-like illnesses were reportedly high in those states.

Experts say accessing this data through nowcasting could improve real-time, geographically precise influenza surveillance. This could be vital to enacting targeted outbreak response measures.

That fancy device on your wrist could someday lead not just to better health for you but for your whole community.