Ramesh Raskar, a computer scientist at the MIT Media Lab, is working on an app that uses GPS to create maps showing the movements of people recently diagnosed with COVID-19. “In an early version, you might see a map with hot spots—2 p.m. at Starbucks, 3 p.m. at the library—that would tell you where people with the disease had recently been,” Raskar told me. “All the government has to do is demand that every test facility release the trails of infected people in an anonymous manner, so that healthy people know where to avoid.”

For privacy advocates, “Waze, but for the sick” might seem harvested from their darkest nightmares. But Raskar is emphatic that his code is open source—“every part of the code should be visible to everybody, every day”—and that no government or tech company would have exclusive control over a centralized database that it could abuse. Users wouldn’t learn anything else about the infected person, such as age or sex.

The technology and privacy challenges of tracing will nonetheless be complex, and could normalize a level of surveillance that might seem totalitarian. If we want to get it right, we should learn from the experiences of other countries. In eastern Asia, tracing has already become a part of daily life. To see a glimpse of America’s future—and to anticipate some of the worst excesses of the technology—it’s useful to briefly review how tracing works across the Pacific.