T. Ryan Gregory πŸ‡¨πŸ‡¦ Profile picture
Dec 27, 2023 β€’ 15 tweets β€’ 3 min read β€’ Read on X
🧡

There are 7 human coronaviruses (so far).

Four of them cause the "common cold" (229E, NL63, OC43, HKU1).

The three most recent are deadly (SARS-CoV, MERS-CoV, SARS-CoV-2).

All three of the deadly ones use the ACE2 receptor. Only one of the common cold viruses (NL63) does.
We have never in the history of our species encountered a situation anything like this one, with a coronavirus that is infecting *billions* of hosts, year-round, repeatedly up to several times per year, and being transported all over the world through mass global travel.
In short, we cannot simply look to other human coronaviruses and draw conclusions about what SARS-CoV-2 will do longer term.

SARS-CoV-2 has already proven itself not to be a "textbook virus". Rather, the textbooks will need to be revised significantly because of it.
Also, here's a reminder that the following are *myths* / *misconceptions*, with no basis in either experience or theory:

❌ That viruses always automatically evolve to become benign so they don't drive their hosts extinct.
Myths / misconceptions cont'd:

❌ That humans have evolved alongside pandemic-level respiratory viruses for millions of years. That's bats. We're not bats. Robin: "Humans evolved with these viruses for millions of ye-"  Batman, striking Robin: "You're not a bat!"
Myths / misconceptions cont'd:

❌ That a virus like SARS-CoV-2 evolves slowly or will soon run out of evolutionary space. This neglects the fact that there is an absolutely enormous population size of the virus and that it is evolving in a changing fitness landscape.
Myths / misconceptions cont'd:

❌ That a pathogen becoming endemic means it is no big deal. Also endemic: malaria, tuberculosis, measles, etc.

nature.com/articles/d4158…
Myths / misconceptions cont'd:

❌ That the immune system is like a muscle that gets stronger with repeated infections and weaker if not exercised through exposure to *pathogens*. Don't confuse this with the "hygiene hypothesis", which is about exposure to *commensal* microbes.
In the same way that we cannot make assumptions about the evolutionary trajectory of SARS-CoV-2 or the effects of (and on) immune systems, we need to reject expectations built on myths and misconceptions.
Every day there are new discoveries about what SARS-CoV-2 does to our bodies. Those proclaiming an end to waves have been proved wrong over and over. Optimistic predictions about the mildness or lack of potential spread of new variants have not survived collisions with reality. No one could have foreseen this.
We do not know what SARS-CoV-2 will do.

There is no simple, linear evolutionary path that it must inevitably follow.

There is no precedent on which to confidently base predictions.

What we can say with some confidence is that more virus is a bad thing.
Quick correction:

MERS-CoV uses the DDP4 receptor, but close relatives of the virus do use ACE2.

The point remains that the deadly viruses are not obviously just cold viruses we're not used to yet.

nature.com/articles/s4142…
(Correction: MERS-CoV uses DDP4 although close relatives do use ACE2. See tweet at the end of the thread.)
Oh, and SARS-CoV-2 doesn't only use ACE2, we are still learning new things about how it can enter cells using different receptors.

nature.com/articles/d4397…
(h/t for the reminder about MERS and DDP4 to @nzm8qs in our variant tracker group!)

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More from @TRyanGregory

Apr 1
It's very important to be clear about what is happening in the Canadian election and how progressives need to approach it. 🧡

The LPC surge toward a majority is due primarily to a collapse of support for the NDP and Bloc, and much less so a drop in support for the CPC.

1/ Vote and seat projections for Canada.
Vote and seat projections for Ontario.
Vote and seat projections for QuΓ©bec.
This means that the Libs are mostly picking up progressive voters who are planning to vote strategically to stop the Cons. They are not picking up huge numbers of "moderate conservatives".

Cons support is generally committed but Libs support isn't.



2/angusreid.org/canadian-elect…
The *winning strategy* for Libs is to make strategic voting by progressives as painless as possible by leaning *leftward*.

The winning approach for progressive voters is to make it clear they cannot be taken for granted and do not agree with rightward drift.

3/
Read 6 tweets
Mar 19
Thoughts on pandemics, inclusion, annexation, Indigenous issues, climate, genocide, and more and the connections I see among them. I fully acknowledge that I am writing this from a position of substantial intersectional privilege.

🧡

1/
I really hoped that the (ongoing) SARS-CoV-2 pandemic would inspire us to make meaningful, positive changes in society. Indeed, early on it seemed like privileged people finally understood what it was like to lack access to things we otherwise take for granted.

2/
Sadly, but perhaps predictably, we instead rushed back to the status quo as quickly as we could. If anything, things are worse now in terms of public health, accessibility and inclusion, and global health equity. Infectious disease has been actively normalized.

3/
Read 10 tweets
Mar 8
Please, stop making these terrible arguments in order to dismiss threats of annexation by the US. 🧡

1. "He's just joking, trolling, negotiating, or being Donald."

Clearly not. Stop it.

1/
2. "Trump can't just declare war on Canada."

He wouldn't bother and he doesn't need to. The last time the US formally declared war was 1942. See every US invasion or occupation since WW2.

2/
3. "The US can't invade because of the constitution / international law."

He doesn't care about either of those things. See everything he's currently doing.

3/
Read 10 tweets
Feb 17
I'm sure infectious disease minimizers are attributing the record-shattering surge of severe flu this year to "immunity debt". Let's think this through, shall we?

🧡

1/
1. Serious mitigations ended more than 4 years ago. Why would immunity debt only kick in now? And why wasn't 4 flu seasons without mitigations enough to repay whatever "debt" there was?

2/
We wrote this more than 2 years ago.

calgaryherald.com/opinion/column…
Read 12 tweets
Feb 16
🧡

Just to recap what is happening, since public health has gone AWOL:

* This is the worst flu season in 15 years. Not just number of cases but number of *severe* cases.

1/
* H5N1 ("avian flu") is getting further out of control in the US. It is getting closer and closer to a human-to-human transmission outbreak.

* Measles is resurgent thanks to low vaccination rates.

* Tuberculosis is making a comeback.

* Many norovirus outbreaks.

2/
* COVID rates are lower than in past winters, but a) they're still way too high to ignore, and b) that's because there was a surge in summer (it's not seasonal) and the next major lineage of variants has not arrived yet.

3/
Read 4 tweets
Jan 18
As you read more and more reports of uncommon pathogens infecting a lot of people, or common pathogens surging far more than usual and/or having unusually severe effects, please remember that this is what immunity theft predicts and what we've warned about for years.

1/
By contrast, "immunity debt" or "post-pandemic normalizing of levels" as an explanation makes less and less sense as more time goes by. In 2025, it is absurd to still be talking of new surges of illness being due to the lack of immunity from mitigations that ended years ago.

2/
Case in point, we wrote this more than 2 years ago.



3/calgaryherald.com/opinion/column…
Read 4 tweets

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