Ten hours. That was how long it took for a virus like Covid-19 to spread from a hospital bed rail to the whole ward.And it stayed there for five days.

This was the finding of a group of researchers who artificially replicated a section of DNA from a plant-infecting virus that cannot infect humans, but which spreads in the same way as SARS-CoV-2 (the virus that causes Covid-19).

The scientists, from London’s University College and Great Ormond Street Hospital, wanted to explore, safely, how quickly Covid-19 can make its way through a hospital...