Trying to Make Sense of that Leaked CDC Model

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May 4, 2020 5:29 p.m.

As you may have sensed from my writing over the last two months I’m if anything a COVID19 pessimist. I have generally thought things would be worse than the consensus opinion anticipated. Unfortunately, I’ve generally been right. But let me strike a different note about this CDC model or forecast that has gotten all the news today. The numbers are stunning. And from a purely non-expert viewpoint they don’t seem credible. I put this forward purely on the basis of being very immersed in the current statistics and having at least some sense of how trends work.

Let me try to explain.

The headlines about this model are that by June 1st the US will be seeing 3,000 fatalities a day and over 200,000 new cases per day. The 3,000 number seems plausible. It’s not that much higher than where we currently are. As recently as April 29th 2700 fatalities were reported in a single day. It’s the rate of new infections that seems very hard to figure. Very hard.

Let me walk through some numbers.

The forecast speaks of more than 200,000 new infection per day. Let’s say it’s 200,000 just to work with even numbers. This would mean that the US was seeing 1.4 million new infections per week. That is substantially more than the number of infections all of the United States has seen since the beginning of the epidemic. This would be upwards of ten times the number of daily infections we’re seeing today. In other words, this assumes we’re going to see an explosion of new cases over the next three or four weeks. As I say, assuming the worst has been a good model of prediction so far. But there’s nothing that I can see in the numbers either nationwide or in individual regions that help these numbers to make sense.

So what does this mean?

One scenario that seems plausible to me is that COVID19 is moving toward critical mass in a lot of parts of the country at once and it is about to explode something like it exploded in the New York metro 4 to 6 weeks ago. Alternatively maybe ‘reopening’ in a bunch of red states is going to lead to a big upsurge. Perhaps it’s a combination of those two things. We don’t really have any visibility into what assumptions went into this model or really anything about it. So we can’t really say what justifies these numbers. But even if we assume these two scenarios the numbers still seem too high.

To be clear, I’m not saying this can’t happen. I mean, seriously, what do I know? It doesn’t seem plausible based on the current trends that it is likely to get that bad that quickly.

Another possibility I considered is that maybe the model is talking about actual infections rather than lab reported ones. We know that the daily new cases tallies we see greatly understate the number of actual COVID19 infections. Indeed, recent serology studies like the one being conducted by New York State suggest that actual infections could be in the range of ten times the number of lab confirmed infections and quite possibly higher. So perhaps this is an estimate of the actual number of new infections per day as opposed to lab confirmed ones?

This seems hard to figure since it’s such an apples to oranges comparison. But there’s one detail that makes me think it’s possible. Remember that estimate of 3,000 fatalities per day? Over time there’s no way that number is consistent with more than 200,000 new cases per day. Perhaps if we’re at the front end of a huge blow up higher fatality numbers could lag into mid or late June. But on their own those forecasts are not consistent. But if the estimate of new infections was a prediction of actual rather than lab confirmed infections they would be much more consistent. And if that were the case it would be more plausible that we would be seeing that number of infections per day at the beginning of June.

If it’s not clear already, I’m doing a lot of speculating here. Please don’t understand this post as more than that. I’m doing so to try to make sense of numbers that on their face seem hard to reconcile even with a pessimistic view of recent trends. What I would say for now is don’t assume that this leaked CDC model is the ‘real’ story we’re not being told. Maybe it is. Or maybe it’s just wrong. Or maybe it’s old. Or based on a set of assumptions that make it unrealistic as a forecast of the coming weeks. I’d say be skeptical.

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