[lamontcg]

> Transmissible diseases usually mutate to be less deadly over time, because killing the host is a bad reproduction strategy.

Incorrect. This virus has already spread by the time you're dying in the hospital and it doesn't "care" if you die or not. If it could spread more effectively during the transmissible period of the disease, while more effectively murdering you on the tail end, it'll murder you more, no problem.

The Delta wave was a good example of the virus mutating to become both more transmissible and lethal, quite successfully from its perspective.

The mechanism for waning virulence is that we've got T-cells which recognize conserved T-cell epitopes so the human race has some level of relatively permanent immunity now against the novel virus, and because immunity to neutralizing antibodies causes the virus to mutate and it is always competing with the immunity to its past self and that has a cost.