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In the book “spillover”, notably written before Covid (so quite prophetic read from today’s perspective), the author discussed this claim. Although it often hap
by rich_sasha 5y ago
In the book “spillover”, notably written before Covid (so quite prophetic read from today’s perspective), the author discussed this claim. Although it often happens, it is by no means guaranteed (at least on satisfactory timelines), and there are counter examples.
One is the evolution of myxomatosis in Australia, it is a disease affecting rabbits. The disease split into 4 strains. Eventually the dominant one become, IIRC, one that had the slowest progression, but also was the deadliest overall.
Buns infected with that strain had larger chances of passing it on (since they were alive longer), and yet they would be more likely to die.
I guess evolution doesn’t care, and if a strain is more deadly, yet more persistent, it will win.
- jacquesm 5y agoThe easier way to look at this is that from the perspective of evolutionary pressure what happens to a host (or parents, for that matter) once reproduction has taken place is irrelevant. So there is no selection pressure for mortality, that's just another outcome, unless it happens too quickly in case the virus has less chance to make it to the next generation. Reductio ad absurdum: if a virus would kill on first contact there would never be any time for it to spread, but once a virus has spread the host is not all that interesting unless it could be caused to continue to spread. So whether the host lives or dies after that won't cause that particular virus to be more or less successful.
- somewhereoutth 5y agoI would go further, and say we have no evidence that any human virus has evolved to become less virulent as it becomes 'endemic'. Instead, susceptible individuals simply die off (e.g. smallpox in the Americas).