Thread by @stgoldst

There's a lot of prediction and uncertainty on the future of #SARSCoV2 in the human population. I'll do a little thread explaining why I *think* it will end up similar to the 4 "common-cold" endemic CoVs, but the time-scale on which this happens is up to us.

There are currently 4 endemic human CoVs: OC43, 229E, NL63, HKU1. OC43 and HKU1 are sort of closely related, same for 229E and NL63. Overall, pretty divergent though. More different than SARS1 and SARS2, for example. They all came from animals, and they all cause mostly

pretty similar, mild disease. We're basically all infected in childhood, more than once. This is probably important. bmcinfectdis.biomedcentral.com/articles/10.11…

These viruses infect us as kids and it's pretty harmless. #SARSCoV2, we all know by now is usually pretty mild in kids. What about the really dangerous CoVs SARS1 and MERS? sciencedirect.com/science/articl…

SARS1 and MERS are notorious for hitting older and sicker folks harder than anyone else. Their age-gradent is severe. They have this in common with #SARSCoV2, but of course many more cases of the latter means more disease for everyone academic.oup.com/cid/article/38…

So if #SARSCoV2 has this in common with SARS1 and MERS, does that distinguish it significantly from the endemic viruses, those mostly harmless ones? It's hard to say since SARS1, #SARSCoV2, and MERS infect people as adults for the first time. We *all* get the endemic viruses

as kids (see above) and basically all have antibodies to them. There are essentially no "immunologically naive" adults infected with endemic CoVs. cvi.asm.org/content/17/12/…

So can we get any insight at all into how the endemic viruses behave in the same types of populations that are so susceptible to #SARSCoV2? It's hard - but we're not totally clueless. An outbreak of OC43 in a nursing home where 8/95 infected residents died ncbi.nlm.nih.gov/pmc/articles/P…

Or an outbreak of NL63 in a long-term care setting where 3/20 patients died. The risk-factors: heart disease, dementia, hypertension, diabetes, and lung disease. Same risk factors as #SARSCoV2 wwwnc.cdc.gov/eid/article/24…

Now, the point here isn't that #SARSCoV2 isn't serious. It's devastating! The point is that a lot of CoVs can be devastating in older and vulnerable populations. When it comes to #SARSCoV2 thats literally hundreds of millions people worldwide. With the other CoVs, it's not

because we start building up immunity as kids and keep doing it with repeated exposure as young adults. So, will #SARSCoV2 end up as "just another endemic CoV"? The truth is, I don't know, but I *think* probably yes - BUT

there's a huge catch. The period of time it took from emergence to mostly harmless for those other viruses may have been years, it could have been a decade! We can't afford that kind of time-span, the death toll, economic toll, and toll on the health of

survivors would be horrific. So we *have* to use the 21st century tools at our disposal to accelerate the time-frame for pushing #SARSCoV2 into this kind of mostly harmless ecological niche. We have to vaccinate - as close to everyone as possible. And we'll need boosters.

The virus will continue to mutate, and multiple exposures are better than 1 or 2 anyway. The good news is vaccine-induced immunity looks better than immunity from natural infection. Science is amazing! We are going to see flare-ups of #SARSCoV2 over time as immunity

wanes among some populations, new variants arise, or when the virus hits communities with low vaccine uptake. That means there will be local or regional needs for public health measures to come back temporarily. We *have* to be prepared to do this.

And the other good news is that even if we don't have vaccines for really little kids soon, the odds are so heavily in their favor with this virus. With aggressive vaccination and public health we can eliminate most of the mortality and morbidity caused by this virus *much*

faster than might happen through a normal course of co-evolution with a new host. I'll close by saying I could be totally wrong and maybe #SARSCoV2 has nothing in common with the endemic CoVs. But I think we throw out existing knowledge at our peril.