Originally Posted by
mattyj
A virus mutating to become less virulent but more contagious is normal
You need to be careful with statements like that.
As viruses mutate the more transmissible mutations tend to dominate because they can outpace their less transmissible forebears in spreading throughout a population. It is unsurprising that the Delta-variant is more transmissible than previous dominant variants but it is largely happenstance that it is less virulent (has a lower case fatality rate).
Ebola, West Nile virus, and the Spanish flu are all examples of viruses that became more virulent after mutating. We also routinely see seasonal flus that are more deadly than their previous strain.