Countries around the world are rolling out contact tracing apps to contain coronavirus. How will we know whether they work?
http://www.sciencemag.org/news/2020/05/countries-around-world-are-rolling-out-contact-tracing-apps-contain-coronavirus-how
Millions of people have downloaded apps designed to alert them to coronavirus exposure. Their effectiveness has yet to be proved.
Science’s COVID-19 reporting is supported by the Pulitzer Center.