Our immune system is the pandemic’s biggest mystery

What have we been witnessing these past few months? A worldwide crisis caused by the arrival of a new virus of exceptional virulence — or a crisis of awareness, in which incomplete information led to a wildly disproportionate reaction? Have lockdowns, face coverings and the rest saved millions of lives worldwide? Or have they had relatively little effect on the course of the pandemic, and ended up causing more harm than good? And why, so far, is Britain not seeing the surge of Covid-19 infections reported in Spain and France? What are we missing?

We still know a lot less about Covid-19, and about viruses in general, than you might have been led to believe. Viruses are older than mankind — and more numerous than all other forms of life put together — but we have only found out about them in the past century. And the sum of what we still don’t know is huge.