How to build and deploy testing systems at unprecedented scale

Editor's note:The Economistis making some of its most important coverage of the covid-19 pandemic freely available to readers ofThe Economist Today, our daily newsletter. To receive it, registerhere. For our coronavirus tracker and more coverage, see ourhub SARS-CoV-2, the virus that causes covid-19, is an unobtrusive piece of biological machinery. It spreads parasitically through the respiratory tracts of human beings, often without provoking symptoms in those who carry it. Yet for some, partic...