Here are the innovations we need to reopen the economy

The second area where we need innovation is contact tracing. Once someone tests positive, public-health officials need to know who else that person might have infected.

For now, the United States can follow Germany’s example: interview everyone who tests positive and use a database to make sure someone follows up with all their contacts. This approach is far from perfect, because it relies on the infected person to report their contacts accurately and requires a lot of staff to follow up with everyone in person. But it would be an improvement over the sporadic way that contact tracing is being done across the United States now.

An even better solution would be the broad, voluntary adoption of digital tools. For example, there are apps that will help you remember where you have been; if you ever test positive, you can review the history or choose to share it with whoever comes to interview you about your contacts. And some people have proposed allowing phones to detect other phones that are near them by using Bluetooth and emitting sounds that humans can’t hear. If someone tested positive, their phone would send a message to the other phones, and their owners could get tested. If most people chose to install this kind of application, it would probably help some.