This might be obvious for most people here but I haven’t found yet a good blog post that I can point out to people repeating something that I have been hearing from the beginning of the pandemic many times, and is false.
Viruses have a natural tendency to evolve towards less deadly forms.
Deadliness is mostly orthogonal to reproducibility. Viruses do not have a tendency to become less deadly unless becoming less deadly makes them also more capable to leave copies of themselves.
In what cases would we see the virus evolving towards less dangerous? In cases where the virus is so deadly that as soon as you are infected, the virus kills you before you had the chance of disseminating copies of the virus to other hosts. In this case, being too deadly is clearly disadvantageous to the virus, so the strains that cause instant death disappear because they cannot propagate to others. It can also happen that a new variant of the virus simply happens to be less deadly and more contagious (which might be the case with the omicron variant), but this is not part of any magical trend where viruses mysteriously evolve until they become the common cold (has HIV evolved towards a less severe disease?). The opposite can happen too. A new strain might appear that happens to be also more contagious and more deadly.
A common misconception about the evolution of viruses
This might be obvious for most people here but I haven’t found yet a good blog post that I can point out to people repeating something that I have been hearing from the beginning of the pandemic many times, and is false.
Deadliness is mostly orthogonal to reproducibility. Viruses do not have a tendency to become less deadly unless becoming less deadly makes them also more capable to leave copies of themselves.
In what cases would we see the virus evolving towards less dangerous? In cases where the virus is so deadly that as soon as you are infected, the virus kills you before you had the chance of disseminating copies of the virus to other hosts. In this case, being too deadly is clearly disadvantageous to the virus, so the strains that cause instant death disappear because they cannot propagate to others. It can also happen that a new variant of the virus simply happens to be less deadly and more contagious (which might be the case with the omicron variant), but this is not part of any magical trend where viruses mysteriously evolve until they become the common cold (has HIV evolved towards a less severe disease?). The opposite can happen too. A new strain might appear that happens to be also more contagious and more deadly.