LogFAQs > #950825391

Yeah, I'm not exactly sure how or why the 1918 flu died down the way it did, though there's likely a similarity reflected in the declining numbers we're seeing from COVID right now.

It didn't hit a level of herd immunity like you'd expect would be needed for its level transmissibility (R0 of 2-3). It only got halfway there at around 30-35% infected worldwide. And a flu vaccine hadn't been created yet. But what you did have is that on top of people who got sick and recovered and became immune, social controls were in place. People wore masks. Behaviors shifted for a time, heading into April of 1920. And I believe what happened was that it was just enough to take the R0 below 1 for long enough that it mutated into a form that was more transmissible, but coincided with lower lethality. Flu's genetic volatility allowed it to escape like this with an ever decreasing number of active infections.

SARS-CoV-2 doesn't really have that level of constraint. It spreads far more easily in warm, humid weather than flu does. But again, its genetically far more stable than flu is. The variant problem in the future won't be nearly as bad as it seems now as long as the effort to track its genetic drift remains strong and vaccinations are applied to defend against them as soon as possible.

I guess what I'm saying is that it will take a concerted vaccination and monitoring campaign to actually eradicate it. But I certainly think it's possible. I think the biggest threat to this is the potential for a very similar coronavirus jumping back out from an animal reservoir, maybe akin to whatever the original source was for SARS-CoV-2.

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Essy