Steven Millman:
November 26th COVID Update: The Thanksgiving Update. Super-Spreader to End All Super-Spreaders
Short version: The Thanksgiving Day festivities look like they will kick off what will be by far the largest moment of disease spread anywhere in the world thus far. Deaths resulting from this will spike leading into Christmas.
tl;dr and amazingly depressing. Might want to skip this one tbh.
You may have heard pundits or medical experts talking about this Thanksgiving as a super-spreader event and begging folks not to celebrate outside of the people they live with. You might be wondering, how bad could this be? Bad. Really, really bad. I mean, Michael Bay with a huge budget bad. Here’s some simple math to help make it clear:
My survey research (the ones recently highlighted on CNBC and in the NY Times) suggest that 27% of Americans plan to attend Thanksgiving dinners with people outside of those they live with and that the average size of these events will be about 7.5 people. More than 60% of those hosting dinners say they are not asking for ANY precautions such as testing or quarantines prior to Thanksgiving. More than 80% of those attending such a dinner say they do not intend to take any precautions.
So let’s now play this out. According to Georgia Tech’s COVID-19 Event Risk Assessment Planning Tool, the probability of at least one person showing up to dinner at Thanksgiving is about 10% nationally and MUCH higher in some areas (lower in others). 27% of Americans is about 89,000,000 people. Divided by 7,5 per Thanksgiving dinner is 11,880,000 dinners where people are interacting with folks outside of their bubble. If ten percent of these have at least one COVID positive individual, that’s 1,180,000 potential spreader events in just that one day. Reduce that by the percent of people who intend to take precautions and that drops to about one million dinners. That’s a lot.
Thanksgiving dinners are essentially best-case scenarios for airborne disease spread. They involve a group of individuals sitting close together and spending several hours together indoors unmasked, often talking loudly. Residential homes do not have powerful ventilation systems and in much of the country it will be far too cold to leave windows open. These are near-perfect conditions for spread of an airborne virus like COVID-19. While it is not known exactly how many people in these homes would become infected, we can make an assumption about reasonable ranges of transmission. An average of one new infection per household where an infected person is present is likely a low-end estimate and an average of three would likely be a high-end estimate of spread. We can see what happens in both ends of this range.
A spread of one new infection per household would create one million new cases and a spread of three new infections per household would create three million new infections on Thanksgiving Day alone as generation one of the spread event. Once again, that’s a lot. Case mortality is just less than one percent, and if we assume 5x infected to cases confirmed, that would yield 200,000 to 600,000 new confirmed cases. Case mortality in the US right now is about 0.9% and climbing, which would yield 1,800 to 5,400 COVID deaths. This is on TOP of existing community spread and BEFORE considering how these newly infected individuals will the spread the disease further. For reference, the worst single day death toll in the pandemic thus far was just over 2,600 according to Johns Hopkins.
A spike in new cases will begin to show up in the data during the first week of December. This super spreader event is expected to be SO MUCH LARGER THAN PRIOR SPREAD EVENTS that it should be visible in the national data in it’s first generation, where all of the other super spreaders (Like Memorial Day and Sturgis) have needed to reach generation 3 or 4 to be seen as more than typical variance.Three weeks later, a visible spike in deaths will start to appear in the national data. That’s the week before Christmas.
These newly infected individuals will also spread the disease to new generations of hosts prior to symptoms appearing which will create a potentially massive 4th surge on the back of what is now, by far, the most explosive period of disease spread since the pandemic began. And if we haven’t learned our lesson by Christmas, we can start talking about the 5th surge.
I should also point out that these numbers are probably very conservative for several reasons. First, I do not take into account the fact that more than three million people are traveling which creates risk for disease spread. Second, there is very likely a correlation between the decision to attend a Thanksgiving under such dangerous conditions and other COVID risk behaviors meaning that the probability that someone shows up to a dinner infected is higher than the national averages. Third, many parts of the country are seeing their health care systems already overwhelmed with the worst of the 3rd surge far from over. This means that the case fatality rate is likely to rise substantially by the time these new sick individuals need intensive care. Finally, one major reason case fatality rates had been falling is that younger folks were the ones most likely to get infected. These Thanksgiving dinners may provide many new infections among the elderly who could then, in turn, spread the virus throughout elder communities.
If we launch new exponential spread these numbers all become immensely more dire.
Thanksgiving will almost certainly be a super spreader event orders of magnitude larger in scale than anything we’ve seen so far and will take place in every corner of the country.
It should go without saying that we should follow the guidance and NOT have Thanksgiving events beyond our own households. It’s not the tradition we look forward to, but if we’re smart we’ll all be here next year to celebrate in a world were spread is low and vaccines abundant. There’s no law against having another Thanksgiving in the summer when you can do it outdoors, right? Hell, I’m going to have a Thanksgiving party as soon as I’m vaccinated. Maybe a few of them. This is American and we can do that if we want to.
Please be safe. Don’t travel in the crowds, wear a mask, remain distanced. Vaccines are coming and we’ll get through this. Just be patient a little while longer.
As always, I’m not a medical professional just a professional statistician that’s not sleeping well.