Duh, that’s what viruses do. Both mutations that make it more transmissions and ones that make it less likely to kill the host cause higher reproduction rates. Therefore, those stations will come to predominate over time.
Also, for something like this that’s marginally lethal in the first place, killing older people and those with comorbidities, after a while, it’s got all the low hanging potential victims.
Transmissible. Stupid auto-corrupt