It may seem surprising, but more than a year after the coronavirus pandemic began, we still don’t know the relative importance of the different ways of catching covid-19: by touching contaminated surfaces or by breathing it in.

In March, UK government advice was that face coverings weren’t generally needed and that people should focus on frequent handwashing, use of hand sanitiser and wiping down surfaces.

Since then, the evidence has mounted that the virus can spread through the air, not only through larger …