How your Fitbit can tell if you're getting sick

The Fitbit on your wrist can not only track your exercise habits, but it can also help tell if you're coming down with the flu - and warn health authorities to get ready to help you recover.

A study in the U.S. found that heart rate and sleep data from the wearable fitness trackers, can predict and alert public health officials to real-time outbreaks of the flu more accurately than current surveillance methods.

Data from more than 47,000 Fitbit users in five American states revealed that predictions of flu outbreaks in those areas were better - and faster.

Traditional surveillance reports can take up to three weeks, meaning response measures, such as deploying vaccines or anti-virals, and advising patients on when to stay home, can take longer.

Previous studies using crowd-sourced data, such as Google Flu Trends and Twitter have experienced variable levels of success.

Experts say that's because it's impossible to separate people with flu from people who search online about it - due to the media and public attention present during outbreaks.

The World Health Organization estimates that as many as 650,000 people die worldwide of respiratory conditions linked to seasonal flu every year.