As the novel coronavirus continues to spread around the world, more governments are relying on mobile carrier data to track everything from patients who should be isolated to how well people are following limited-movement edicts.

Mobile carriers in the European Union are sharing data with health authorities in Italy, Germany, and Austria to help monitor whether people are following instructions to maintain social distances and stay close to home during the outbreak, Reuters reports.

The European Union’s General Data Protection Regulation, or GDPR, limits how companies can share and manage customers’ personal data. The location data currently being shared by cellphone providers is anonymous and aggregated, per the GDPR rules. In Italy’s Lombardy region, the first major swath of the country to be placed under lockdown, the mobile data is reportedly helping authorities get a clearer picture of how well people are observing the rules, according to Reuters, showing movement is down by about 60 percent in the past month.

On March 16th, Israel authorized the use of cellphone location data to track the virus. The country’s internal security agency, the Shin Bet, has collected data from mobile carriers since about 2002. Prime Minister Benjamin Netanyahu authorized the Shin Bet to track the movements of patients who have tested positive and to determine who should be under quarantine.

An Israeli security official told The New York Times that the data was going to be used in a “focused, time-limited and limited activity.”

South Korea used location data to make a public map of coronavirus patients

Other countries are using location data from cellphones to track the pandemic in different ways, from an app called AC 19 in Iran to China’s tracking system that sends information to law enforcement officials, to Taiwan’s “electronic fence” that alerts authorities when a quarantined person moves too far away from their home. As of Monday, Taiwan had 195 confirmed cases of the novel coronavirus, one of the lowest tallies of any country.

Perhaps the most aggressive use of cellphone location tracking is happening in South Korea where the government has created a publicly available map from cellphone data that people can use to determine if they have come into contact with someone who has been infected with the novel coronavirus. South Korea is viewed as something of a success story in its efforts to beat back the spread of the virus; the BBC reports that the country recorded 64 new cases in the past 24 hours, down from its peak of 909 cases reported on February 29th.

South Korea’s health authorities have been sending detailed text messages that range from reminders about handwashing to specific information about people who have tested positive and where they are, The Guardian reports. An example text message read “A woman in her 60s has just tested positive. Click on the link for the places she visited before she was hospitalized.” The link directs to a list of locations the person visited before she tested positive, according to The Guardian.

Of course, tracking the movements of patients who have been infected with the novel coronavirus and people who haven’t has raised myriad privacy concerns, and how effective the methods are may never be totally known. If a person doesn’t want to be tracked, they can disable location settings on their device or turn their phone off altogether.

Whether the US would track user data in a similar way remains unclear, but the federal government is reportedly in “active talks” with Facebook, Google, and other tech companies, according to The Washington Post.