Theory you citing is not that credible. Smallpox virus was with humanity for at least 3500 years. In XX century it's lethal rate was about 30% for adults, more for children.
> Take-home message:
> - The idea that viruses always evolve to become less lethal because it is advantageous to them is an old theory that has been shown to be wrong
Thank you for correcting a misconception of mine! :D
[1] https://www.mcgill.ca/oss/article/covid-19/do-bad-viruses-al...