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Originally Posted by Marcellus
We have been told from day 1 with viruses that they mutate to more transmittable and less deadly correct?
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Mutations that are more transmittable are strongly selected for. So for instance, when you have half the population vaccinated but the virus is still widely circulating, there will be strong selection pressure for the virus to mutate to a version that will evade the vaccine.
And when the virus is circulating in a population where some already have some immunity from already having had it, again there will be selection pressure to mutate to a form that can reinfect.
The pressure to be less deadly isn't necessarily as strong. If the person is most infectious at the beginning of the illness, then it doesn't really make the virus that more transmissible if the person lives or dies at the end. But over the long term, the expected trend would be toward less deadly.