Governments in China, Singapore, Israel and South Korea that are already using such data credit the practice with helping slow the spread of the virus. The U.S. and European nations, which have often been more protective of citizens’ data than those countries, are now looking at a similar approach, using apps and cellphone 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 to create a shared system that could take uploads from apps in different countries. “If somebody gets sick, we know who could be infected, and instead of quarantining millions, we’re quarantining 10.”

The U.S. federal government, working with the Centers for Disease Control and Prevention, is creating a portal that will compile phone geolocation data to help authorities predict where outbreaks could next occur and determine where resources are needed, though the effort faces privacy concerns.

The anonymized data from the mobile-advertising industry shows which retail establishments, parks and other public spaces are still drawing crowds that could risk accelerating the transmission of the virus. Alphabet Inc.’s Google said Thursday it would share a portion of its huge trove of data on people’s movements.