How Apple Watch can know when you’re sick days before actual symptoms

With the new Vitals app, Apple Watch users can quickly view key overnight health metrics, receive alerts when two or more metrics are out of their typical range, and gain better context when it comes to their health.

Apple Watch users have been pleasantly surprised to find that the Vitals app, part of the latest watchOS update, can now predict potential illness. According to Reddit posts, the app has been able to detect signs of illness in users up to three days before they experience symptoms.