The U.S. and Europe are moving toward unprecedented cellphone surveillance strategies to track residents infected with the coronavirus as a way to slow the spread of the disease, The Wall Street Journal reported Friday.

The practice, which has been put in use in China, Singapore, Israel and South Korea, has faced a tougher audience in European countries and the U.S. because of privacy concerns.

Still, more governments are looking into data surveillance as a way to keep coronavirus cases in check, as U.S. cases topped 257,000 on Friday, according to Johns Hopkins University data.

“I think that everything is gravitating towards proximity tracking,” said Chris Boos, a member of Pan-European Privacy-Preserving Proximity Tracing, a project that is working on developing a shared system that can receive uploads from phone apps in different countries. “If somebody gets sick, we know who could be infected, and instead of quarantining millions, we’re quarantining 10.”

The federal government is working to create a portal combining phone geolocation data to aid authorities in finding and predicting where future outbreaks of the virus will occur and what resources would be needed.

The anonymous data from the mobile-advertising industry would show officials at places like the Centers for Disease Control and Prevention which locations, like retail stores or parks, people are still gathering during the pandemic. Google said on Thursday it would share portions of its data with the federal government for that purpose.

In Europe, surveillance measures are more overt, as governments are encouraging citizens to install tracking apps.

The Slovakian government passed a law last week allowing its public health office to collect phone data, the Journal reported.

“We realize that this is an infringement of fundamental rights and freedoms, let’s not pretend it is not,” Slovakian Justice Minister Mária Kolíková reportedly said. “In a democratic state, an interference with fundamental rights and freedoms is possible if the measure is proportionate to the purpose.”

Public health experts say that without a vaccine, location-tracking could be an effective way to mitigate the spread of the coronavirus and could help with mass testing, providing governments with a better sense of the infected population.