3 ms·

> Why less deadly? Because a virus that is too deadly will likely die. It's why the Spanish flu is now just H1N1. Given how slowly SARS-CoV-2 kills you (if it

> Why less deadly? Because a virus that is too deadly will likely die. It's why the Spanish flu is now just H1N1. Given how slowly SARS-CoV-2 kills you (if it does), there isn't any selection pressure to do it less often. Indeed, my understanding is that no human virus has evolved to become less virulent. It is unclear why H1N1 disappeared a few years after it emerged as the Spanish flu, most likely it simply ran out of susceptible hosts. In particular, we have no evidence of a successor virus, evolved from H1N1, that was both less virulent and drove out H1N1 at that time. I agree that annual shots are a very real possibility. I also share your pessimism about our response to global warming.

cletus 5y ago
Think about it this way: what is the evolutionary pressure for it to become more lethal? Particularly if we accept your premise that such lethality occurs after it spreads. Now a given strain may mutate to become more deadly but why would such a strain become dominant? Even if all this occurs after the virus can spread, consider the human reaction to it. You have two diseases: one is essentially the common cold, the other is basically Ebola. Even if those events occur after transmission, the response to each disease is going to be wildly different. The common cold will just be tolerated and managed. There will be no lockdowns. The second will have the military enforcing lockdowns and curfews combined with hard travel borders and checkpoints. There would be forced vaccination in some places and severe restrictions on the voluntarily unvaccinated. Just the human reaction alone will tend to make the common cold version more dominant over a sufficiently long time frame.
- somewhereoutth 5y ago
  I don't think it quite works like that - human reaction would affect the transmission of both the original 'bad' variant, and a hypothetical 'good' variant equally. It wouldn't induce a selection pressure favouring one over the other. Furthermore, even with ICUs overflowing, a large segment of the population considers it 'just the flu' - and likely still would even if it became more virulent. After all, their assessment is based on ideology, party affiliation etc rather more than cold facts.
Izkata 5y ago
> Indeed, my understanding is that no human virus has evolved to become less virulent. It is unclear why H1N1 disappeared a few years after it emerged as the Spanish flu, most likely it simply ran out of susceptible hosts. In particular, we have no evidence of a successor virus, evolved from H1N1, that was both less virulent and drove out H1N1 at that time. Spanish flu is still around and did become less virulent over time - and it has descendants that comingled with other flus to create other pandemics: https://www.history.com/news/1918-flu-pandemic-never-ended https://www.history.com/news/1918-flu-pandemic-never-ended
- somewhereoutth 5y ago
  Indeed H1N1 has popped up from time to time, with varying outcomes, not least as prior immunity waned. We are also much better at treating people, particularly bacterial coinfections. Flu is a bit peculiar with viral RNA/DNA (I forget which) reassortment. However it did not fade out or transmute at the end of the 1918 pandemic due to a selection pressure to become less lethal (or at least, we have no evidence that that is the case)

cletus 5y ago

Think about it this way: what is the evolutionary pressure for it to become more lethal? Particularly if we accept your premise that such lethality occurs after it spreads. Now a given strain may mutate to become more deadly but why would such a strain become dominant? Even if all this occurs after the virus can spread, consider the human reaction to it. You have two diseases: one is essentially the common cold, the other is basically Ebola. Even if those events occur after transmission, the response to each disease is going to be wildly different. The common cold will just be tolerated and managed. There will be no lockdowns. The second will have the military enforcing lockdowns and curfews combined with hard travel borders and checkpoints. There would be forced vaccination in some places and severe restrictions on the voluntarily unvaccinated. Just the human reaction alone will tend to make the common cold version more dominant over a sufficiently long time frame.

somewhereoutth 5y ago
I don't think it quite works like that - human reaction would affect the transmission of both the original 'bad' variant, and a hypothetical 'good' variant equally. It wouldn't induce a selection pressure favouring one over the other. Furthermore, even with ICUs overflowing, a large segment of the population considers it 'just the flu' - and likely still would even if it became more virulent. After all, their assessment is based on ideology, party affiliation etc rather more than cold facts.

Izkata 5y ago

> Indeed, my understanding is that no human virus has evolved to become less virulent. It is unclear why H1N1 disappeared a few years after it emerged as the Spanish flu, most likely it simply ran out of susceptible hosts. In particular, we have no evidence of a successor virus, evolved from H1N1, that was both less virulent and drove out H1N1 at that time. Spanish flu is still around and did become less virulent over time - and it has descendants that comingled with other flus to create other pandemics: https://www.history.com/news/1918-flu-pandemic-never-ended https://www.history.com/news/1918-flu-pandemic-never-ended

somewhereoutth 5y ago
Indeed H1N1 has popped up from time to time, with varying outcomes, not least as prior immunity waned. We are also much better at treating people, particularly bacterial coinfections. Flu is a bit peculiar with viral RNA/DNA (I forget which) reassortment. However it did not fade out or transmute at the end of the 1918 pandemic due to a selection pressure to become less lethal (or at least, we have no evidence that that is the case)