> Mutations aren't a serious concern. Because when viruses mutate it's the strains that are more infectious and less lethal that win out.
If only it worked that way! It doesn't, of course.
A random walk can lead anywhere in the adjacent landscape. That includes moving up in lethality without moving down in infectiousness. What you have written here is plausible-sounding nonsense; if it were true, the 1918 flu would never have occurred.
The good news is that influenza is almost pathologically mutation-prone, and coronaviruses are not.
The oft-cited theory about 1918 is that WWI upended the traits that were selected for in the virus. Whereas in peace time a more serious case would reduce the mobility of the victim, in war a serious infection would result in the patient (a soldier) being transported off the front lines, spreading the more serious version of the virus more.
Moving up in lethality while maintaining the same "infectiousness" still results in a real-world decrease in infection rate, as more infected hosts will die (and/or infected hosts will die more quickly), preventing them from spreading it further.
In the case of COVID-19, which is highly contagious, has a long latency period, and is in fact not especially fatal by the standard of diseases ending in -RS, this might be true on paper, but would be cold comfort in practice.
If only it worked that way! It doesn't, of course.
A random walk can lead anywhere in the adjacent landscape. That includes moving up in lethality without moving down in infectiousness. What you have written here is plausible-sounding nonsense; if it were true, the 1918 flu would never have occurred.
The good news is that influenza is almost pathologically mutation-prone, and coronaviruses are not.