I think this doesn’t quite change everything, for the following reasons:
Even if long-term immunity is unlikely, short-term immunity will push this back towards the flu category, where most people are not getting it acutely at the same time. This will significantly improve the healthcare situation vs what we’re seeing in the pandemic phase.
Diseases evolve towards increased spread, which usually involves evolving towards reduced lethality / severity. If this becomes endemic it’s likely to do the same.
If it turns out that this does become a severe endemic disease, there will be a lot of pressure on the development of a vaccine, much more so than has been true for human coronaviruses in the past (when they were much closer to being mostly a nuisance, and included in the general “common cold” category.) Even if long-term immunity is unlikely, we can still improve the situation like we currently do with influenza, giving people periodic boosters based on the current circulating strains.
Diseases normally evolve toward increased spread by reducing lethality because they don’t have a superpower like Covid2019′s ability to spread while the carrier is asymptomatic. I don’t think there’s much evolutionary pressure on this disease toward lower severity. Even if we do a good job of enforcing shelter-in-place in populous areas, there will be hidden reservoirs until we reduce the number of new cases in connected communities all the way to zero.
The normal evolutionary pressure works because there’s some variation between different strains, and whichever variant can reach the most people comes to dominate. With a normal infection, once everyone is aware, you can quarantine people with evident symptoms and thus squelch the spread. Any variant that has milder symptoms has a better chance of spreading and becoming dominant. Covid2019 already has the ability to escape surveillance if there’s any of it in the population, so a less lethal variant doesn’t have a selective advantage.
That’s a good answer, and consistent with this very good article by Johns Hopkins epidemiologist Justin Lessler. He makes many of the same points you make, and adds that there will likely also be partial immunity even within individuals. (At least, I suppose, if we aren’t facing antibody-dependent enhancement.)
I think this doesn’t quite change everything, for the following reasons:
Even if long-term immunity is unlikely, short-term immunity will push this back towards the flu category, where most people are not getting it acutely at the same time. This will significantly improve the healthcare situation vs what we’re seeing in the pandemic phase.
Diseases evolve towards increased spread, which usually involves evolving towards reduced lethality / severity. If this becomes endemic it’s likely to do the same.
If it turns out that this does become a severe endemic disease, there will be a lot of pressure on the development of a vaccine, much more so than has been true for human coronaviruses in the past (when they were much closer to being mostly a nuisance, and included in the general “common cold” category.) Even if long-term immunity is unlikely, we can still improve the situation like we currently do with influenza, giving people periodic boosters based on the current circulating strains.
Diseases normally evolve toward increased spread by reducing lethality because they don’t have a superpower like Covid2019′s ability to spread while the carrier is asymptomatic. I don’t think there’s much evolutionary pressure on this disease toward lower severity. Even if we do a good job of enforcing shelter-in-place in populous areas, there will be hidden reservoirs until we reduce the number of new cases in connected communities all the way to zero.
The normal evolutionary pressure works because there’s some variation between different strains, and whichever variant can reach the most people comes to dominate. With a normal infection, once everyone is aware, you can quarantine people with evident symptoms and thus squelch the spread. Any variant that has milder symptoms has a better chance of spreading and becoming dominant. Covid2019 already has the ability to escape surveillance if there’s any of it in the population, so a less lethal variant doesn’t have a selective advantage.
My understanding is that asymptomatic spread is pretty common.
That’s a good answer, and consistent with this very good article by Johns Hopkins epidemiologist Justin Lessler. He makes many of the same points you make, and adds that there will likely also be partial immunity even within individuals. (At least, I suppose, if we aren’t facing antibody-dependent enhancement.)