New systems to track who is infected and who isn’t, and where they’ve been, have been created or extended in China, South Korea and Singapore. And a range of other surveillance systems – some utilizing GPS location data, some gathering medical data – have been debated or piloted in Israel, Germany, the U.K., Italy and elsewhere.

The challenge: achieving the tricky balance between limiting the spread of disease and allowing people freedom to move outside their homes.

Whether the prospect on the table is “immunity passports” or cellphone-based tracking apps, the aim is to protect public health. But experts say it’s also important to avoid a slippery-slope scenario where data collected to minimize the spread of disease is stored indefinitely, available without limits to law enforcement or susceptible to hackers.

“We need to build necessary guardrails for civil liberties,” said Jake Laperruque, a lawyer at the nonprofit Project on Government Oversight in Washington. “If new data is being collected for public health purposes, it should only be used for public health purposes.”