Smartwatches can do much more than count steps, with research showing they can detect coronavirus infections days before diagnosis.

One of the keys to combatting coronavirus is early detection and diagnosis. The faster someone is diagnosed, the faster they can be quarantined and the less likely they are to spread the virus to others. Adequate testing has long been a major problem, making it difficult to get the pandemic under control. Adding to the challenge is COVID-19’s long incubation period, as well as the fact that patients can transmit the disease before they are visibly symptomatic.

According to CBS News, researchers at Mount Sinai Health System in New York and Stanford University in California have shown that wearable devices — such as the Apple Watch, Fitbit and Garmin — can detect coronavirus before symptoms appear and even before tests can detect it.

The key is in detecting minute changes in a wearer’s heart rate, skin temperature and other physiological markers. In particular, heart rate variability is a key factor. Heart rate variability measures the time between heartbeats, and is impacted by the state of a person’s immune system.

“We already knew that heart rate variability markers change as inflammation develops in the body, and Covid is an incredibly inflammatory event,” Rob Hirten, assistant professor of medicine at the Icahn School of Medicine at Mount Sinai told CBS MoneyWatch. “It allows us to predict that people are infected before they know it.”

The findings could be another important step in the fight against the coronavirus pandemic, and will likely lead to a jump in wearables demand.