Generally agree, but I would think that some kind of “new waves” scenario has a much higher than 1% probability given that it’s how influenza and many other seasonal viruses continue to circulate. That said, in many “new waves” scenarios we are able to create seasonal vaccines or otherwise mitigate the effects. This may result in a permanent drag on economic growth without reducing growth below 0 (collapse).
Once enough people have been infected and recovered, gaining immunity, the evolutionary pressures on a virus switch from “spread as fast as possible into new hosts” to “keep the current host alive and infectious long enough to encounter a host without immunity”. Even though influenza periodically bypasses existing immunity, the evolutionary pressure towards lower mortality is still present most of the time. In particular, our actions to quarantine and isolate, if sufficiently widespread, will also put a lot of evolutionary pressure towards less-severe effects on SARS-CoV-2. All those mild and asymptomatic cases? Pretty soon those are going to be the most successful replication strategy, and the SARS-CoV-2 population as a whole will be pushed towards causing lower mortality.
There is still a chance we’ll have repeated high-mortality waves, but one should note that coronaviruses and influenza viruses are not particularly closely related. Influenza seems to have about one mutation in its protein coat per replication, while as of Feb. 11th the 81 sequenced samples of SARS-CoV-2 had “at most seven mutations relative to a common ancestor”. So I’m inferring that SARS-CoV-2 is less likely to be able to bypass existing immunity on a yearly basis. Influenza has a high mutation rate due to lacking RNA proofreading enzymes, so if SARS-CoV-2 has an RNA proofreading enzyme or hijacks host-cell proofreading enzymes I would also update towards a lower probability of repeated waves. Influenza is also unusual because it’s composed of eight pieces of RNA, which makes it easy for different strains of influenza to swap genes when they infect the same cell at the same time. This is another major reason that influenza bypasses immunity so often. SARS-CoV-2 seems to have one 30,000 base-pair segment of RNA, so it can’t do that trick either.
There are still a lot of unknowns, but so far there’s no evidence I’ve heard of which has made me update towards SARS-CoV-2 being more likely to be able to bypass existing immunity than other coronaviruses, much less influenza.
Coronaviruses in general, including the original SARS-CoV, do indeed have proofreading enzymes, which is why their genomes are so unusually stable (and hence so unusually large) for RNA viruses.
I didn’t dig down on the SARS-CoV-2 genome yet (I only started looking into this in depth yesterday) but a quick search suggests that the proofreading exonuclease is indeed there.
Generally agree, but I would think that some kind of “new waves” scenario has a much higher than 1% probability given that it’s how influenza and many other seasonal viruses continue to circulate. That said, in many “new waves” scenarios we are able to create seasonal vaccines or otherwise mitigate the effects. This may result in a permanent drag on economic growth without reducing growth below 0 (collapse).
Once enough people have been infected and recovered, gaining immunity, the evolutionary pressures on a virus switch from “spread as fast as possible into new hosts” to “keep the current host alive and infectious long enough to encounter a host without immunity”. Even though influenza periodically bypasses existing immunity, the evolutionary pressure towards lower mortality is still present most of the time. In particular, our actions to quarantine and isolate, if sufficiently widespread, will also put a lot of evolutionary pressure towards less-severe effects on SARS-CoV-2. All those mild and asymptomatic cases? Pretty soon those are going to be the most successful replication strategy, and the SARS-CoV-2 population as a whole will be pushed towards causing lower mortality.
There is still a chance we’ll have repeated high-mortality waves, but one should note that coronaviruses and influenza viruses are not particularly closely related. Influenza seems to have about one mutation in its protein coat per replication, while as of Feb. 11th the 81 sequenced samples of SARS-CoV-2 had “at most seven mutations relative to a common ancestor”. So I’m inferring that SARS-CoV-2 is less likely to be able to bypass existing immunity on a yearly basis. Influenza has a high mutation rate due to lacking RNA proofreading enzymes, so if SARS-CoV-2 has an RNA proofreading enzyme or hijacks host-cell proofreading enzymes I would also update towards a lower probability of repeated waves. Influenza is also unusual because it’s composed of eight pieces of RNA, which makes it easy for different strains of influenza to swap genes when they infect the same cell at the same time. This is another major reason that influenza bypasses immunity so often. SARS-CoV-2 seems to have one 30,000 base-pair segment of RNA, so it can’t do that trick either.
There are still a lot of unknowns, but so far there’s no evidence I’ve heard of which has made me update towards SARS-CoV-2 being more likely to be able to bypass existing immunity than other coronaviruses, much less influenza.
Coronaviruses in general, including the original SARS-CoV, do indeed have proofreading enzymes, which is why their genomes are so unusually stable (and hence so unusually large) for RNA viruses.
I didn’t dig down on the SARS-CoV-2 genome yet (I only started looking into this in depth yesterday) but a quick search suggests that the proofreading exonuclease is indeed there.