My Model of the New COVID Strain and US Response

Cross-posted from Putanumonit, I will likely keep the post more up-to-date there than on here as my estimates change. This was also intended for a non-LW audience, since smarter people than me have provided their estimates here and you shouldn’t overweight me because I have my own blog. I am including some new info and analysis that wasn’t in Zvi’s post, so update accordingly.


There is evidence of a new highly-infectious strain of COVID-19 emerging in the UK and other countries. This post is an elaboration of my current model of it, as promised in my review of LessWrong’s collection on Epistemology. Most of the information I have on this new COVID variant comes from this post by Zvi, the links from it, and comments. Read those if you haven’t yet.

Though I usually strive to have timeless content on my blog, I’m making another COVID exception. I’ve heard from dozens of people who were able to prepare for COVID’s first outbreak as a result of reading Seeing The Smoke, and this post may end up even timelier than the last. I anticipate both my model and the evidence to change rapidly, everything below is a snapshot of what I believe as of Christmas Day 2020. Reminder: I am not an expert on this even compared to other non-experts in the LessWrong comments.


The median prediction on Zvi’s LW post is around 60% that the new variant is at least 50% more transmissible and same for there being a third COVID wave in the US:

I would add a few things without straying too far from the crowd’s wisdom.

First, I would revise the crowd’s estimate for the first question down for no other reason than that the poll came at the end of a post titled We’re Fucked, It’s Over. If ever there was going to be a framing effect pushing estimates upwards, this would be it. There are also more alternative explanations for the information coming out of the UK than Zvi accounted for.

Instead of just saying that that there’s a 60% chance it has a 50% higher transmissibility, I would break it down something like this:

  • 35% that the new strain is a nothingburger.

  • 30% that it’s slightly more transmissible, say with an effective reproduction rate (rt) 20% higher.

  • 30% that it’s significantly more transmissible, e.g. 70% higher.

  • 5% in the Captain Malcolm Reynolds probability bucket.

I also believe it very likely that new variant is already present in the US, given that a dozen flights from London have landed in NYC just in the last week. Travel from the UK has been restricted on Christmas eve but the dust from the bolting horse has already settled by the barn door.

A variant that’s just 20% more infectious will still take over exponentially from the old variant resulting in a chart like the one we see.

Several people have tried to explain away the growth of the new variant as being due to things like catching a superspreader, but it doesn’t have to be one or the other. It could have rt=1.2 and catch a superspreader event to make it look like rt=1.5-1.7. This is why I am giving extra weight to the hypothesis of slightly higher transmissibility.

I also think there’s a huge difference between rtnew=1.2 and rtnew=1.7 (here I mean rt relative to the old strain given the same measures of containment) in terms of outcomes.

In the first case, to keep the virus suppressed (i.e. r<1) we need to take measures that would have yielded rt=0.8 for the old strain. New York sustained that number (albeit never dipping below 0.7) for two months running in the spring. Given that ~30% of the state has already been infected, that makes this all the more doable. Gyms and restaurants will close and people will grumble, but we’ll probably survive till the vaccine.

rtnew=1.7 is an entirely different case. Suppressing it would require the sort of lockdown that would yield rt=0.6 for the old strain, a number that has never been reached by any US state for any amount of time. I see no way in hell that Americans would agree to a lockdown much stricter than any we’ve had so far, especially after they’ve been promised that the worst is behind them.

Rural red tribers will not agree because Biden is in the White House. Urban blue tribers because containment in cities is much harder anyway. Young people will not agree because the virus harms them less than the lockdown. Dumb people will not agree because they will not understand the science and math and smart people, seeing that, will try to get infected early before the hospitals are overwhelmed.

No one will believe any of the “experts” at the CDC or WHO or Dr. Fauci because they have all repeatedly lied and tried to manipulate people and reversed their positions without admitting that they have. They all have negative credibility at this point with many Americans.

If the new virus is 1.7 times as infectious I believe that Americans will most likely simply give up on containment, the populace if not the government. We’ll have time to vaccinate the most vulnerable 10-20% of the population by April-May, at which point the majority of everyone else will get the new strain.

There is a small chance that the US will get its shit together vaccine-wise and beat the new strain in a race. Israel, for example, has a simple system in place to vaccinate the vast majority of its 9-million strong population by the end of March. On this timetable, even a virus with rt=1.7 will not have time to explode before herd immunity kills it.

The same is not true of the US, which is currently projected to reach majority immunization no earlier than the late summer by refusing to do basic things to rush the process.

And what’s the Captain Mal bucket?

The new variant being more virulent in addition to being more infectious. Another newer strain that’s even worse. Or, in a nightmare scenario, a highly-transmissible mutation that also renders the Pfizer and Moderna vaccines ineffective.

If COVID has taught us one thing, it’s that it’s all usually worse than we thought.

So the bottom line is that I currently estimate a 30-35% chance of us being truly fucked, in the sense of dozens of millions more Americans getting COVID in 2021 and hundreds of thousands more dead, along with local attempts at extreme lockdowns. I’m not going to speculate on the further implications of this for things like financial markets or the fabric of our civilization. I also anticipate that I’ll be revising these numbers in the next few days.

Merry Christmas.