Covid Isn't Killing Minnesotans Like It "Should"

I know we've all been distracted by the riots (I know I have), but a lot more people died of covid-19 during the riots than were killed in the rioting. The new coronavirus remains our state's biggest problem (albeit no longer our most urgent).

A couple of weeks ago, in a short piece called "Expected Daily Covid Deaths in Minnesota (May)" I grabbed the Minnesota Model source code, ran the model, and I told you how many people we expected to die of covid-19 through the end of May.

Well, May is now over, and we have our results:

DateProjected DeathsActual Deaths
Before 13 May55761413 May29.02414 May30.32515 May 31.72016 May 33.11717 May 34.62218 May 36.1919 May 37.71720 May 39.32921 May 41.13222 May 433323 May 45.21024 May 47.61725 May 50.51226 May 53.71827 May 57.43328 May 61.43529 May 65.92930 May 70.73031 May 75.914TOTAL1441.11040

As I wrote at the time,

The uncertainty on this seems to be in the neighborhood of +/- 300, based on Slide 12 here. That means anything from 1100 to 1700 deaths should be considered a success for this model.

...If we end up significantly below this death toll (under 1100), then it means the model is missing something... Perhaps the new treatments we've started receiving are really effective, or perhaps summer weather is having a substantial effect on slowing the virus's spread. (The Minnesota model does not include weather in any way.) Or, more cynically, perhaps it means people are dying at home and not getting discovered. I've become a lot more pessimistic about these things since Minnesota gave up on test/trace/isolate and Virginia got caught cooking its books.

Well, here we are. COVID-19 is not killing people as quickly as it "ought" to be. It's still offing us at a good clip, to be sure, but the number has held pretty steady during a period when the number should have doubled. (Something similar seems to be happening with our overall case count, although I haven't subjected it to rigorous analysis.) Why?

I don't know.

Covid skeptics (who have been saying all along that covid was never going to kill that many people) have argued that, once we realized how many people had already had covid and how close we were to herd immunity, we would also realize that covid was never that deadly to begin with. The high-caliber gun who favors this position is John Ionnadis, but I find him unconvincing for reasons laid out here, here, and, quite loosely, here.

I still quite like the theory that, as summer approaches, covid is simply losing steam. This was a hope we had early on, which gradually faded, but maybe there's something to it after all. The problem with this theory is that I have very little evidence to support it. It's basically this Canadian study and not much else.

I don't find it plausible that Minnesota is missing something like half of all covid deaths. I'm sure we're missing some, but not to that extent.

I find it plausible but not likely that this was just an outlier outcome. The Minnesota Model always entertained substantial uncertainty, and maybe we just fell a little outside their 95% confidence interval, which should happen sometimes. But the reason we have those confidence intervals is precisely so that, when we fall outside them, we have a signal that something is probably wrong.

Another popular theory among the skeptics is that we aren't properly adjusting our infection-fatality estimates based on who has mostly been infected so far, namely (according to covid skeptics) old people. I find this more plausible. First, we really don't have a lot of details on the demographics of who has been infected so far -- it's been hard enough getting seroprevalence studies going that tell us how many people have been infected so far, period. (EDIT: We do have more details than this sentence misleadingly implies. See Minnesota's infections dashboard, for example.) So there's not a lot of evidence for this claim that I can find, but also not a lot of evidence against. Second, I find this plausible because a lot of the states with high death rates (including Minnesota) have had a terrible habit of shipping still-infected elderly people back to their nursing homes after hospitalization. And it seems to me, without looking at the figures too closely, that those states started seeing dramatic improvements in their death rates (vs. projections) as soon as they stopped doing stupid things to the elderly like that and started intense testing, tracing, and isolation within nursing homes.

If this hypothesis is true, it's unclear what it means for the epidemic going forward -- are nursing home patients developing herd immunity? Does that mean the epidemic for the rest of us isn't coming, or is simply coming more slowly? How many casualties can we expect if previous fatality rate estimates were not properly age-stratified? (NOTE: it sure seems to me that previous case fatality rate estimates were properly age-stratified, thinking especially here of the Verity et. al. study that was treated as canonical for a number of weeks... but infection fatality rates maybe not, I'll have to check.)

Bottom line, though: I don't know. I just know that Minnesota's model made a prediction about how this virus was going to spread through the end of May, and the prediction was wrong, which means one or more of its assumptions was wrong as well. No shame in that, that's science -- but we should figure it out as fast as we can, because, in this case, public policy does not have time to wait for the science process to fully play out.

It is inevitable that we will get some things wrong in our response to the pandemic, because we just don't understand the virus very well yet... but there are enormous costs to getting them wrong, and we must change course immediately if it's warranted.

Other Silver Linings

Having giant, non-socially distanced riots in the downtown streets gives us a pretty handy natural experiment in covid transmission. If our case load suddenly accelerates over the next three weeks or so, then that tends to confirm some of our fears about the virus. But if our epidemic doesn't accelerate, especially compared to other similarly-situated cities that did not experience riots, then that seems to confirm that outdoor transmission of covid is more or less impossible, at least in summer weather. If that happens, we should pretty much throw the idea of outdoor social distancing in the trash bin, reopen the pools, and go about our summer. (It'll take more than that to make me feel safe indoors with strangers, though.)