The pandemic has been awash with slogans, but in recent weeks, two have been repeated with increasing frequency: “Variants will evolve to be milder” and “Covid will become endemic”. Yet experts warn that neither of these things can be taken for granted.

Those stating that viruses become less deadly over time often cite influenza. Both of the flu viruses responsible for the 1918 Spanish flu and 2009 swine flu pandemics eventually evolved to become less dangerous. However, the 1918 virus is thought to have become more deadly before it became milder. And other viruses, such as Ebola, have become more dangerous over time.