| Welcome back to COVID in Minnesota TODAY, an email newsletter from MPR News about understanding the latest developments in Minnesota's COVID-19 outbreak. | | |
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My projected peak has not yet come, and with each passing day I become both more wrong and less optimistic.
Minnesota's current COVID-19 wave right now stands upon the edge of a knife. Some metrics suggest that we're due for a peak sometime soon. Other factors are sending more concerning signals, especially in conjunction with external events that could spur transmission.
I don't have firm answers for you here, but I'll do my best to lay out what we know and what that might mean. |
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Three things to know
| - The growth in key COVID-19 metrics has been slowing, but sometimes erratically, so it's unclear when a peak might arrive
- This current wave is lasting longer than past waves, with several possible explanations
- Vaccinations rose in August, but still fell far short of rates from earlier this year
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| We're up to around 1,500 confirmed cases per day, on average, up from 1,200 per day one week ago and 1,000 per day two weeks ago. | | |
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On the one hand, that's bad — cases are still going up.
On the other hand, you'll notice there's not a ton of acceleration going on. Cases are up 50 percent over the last two weeks, which compares to 70 percent seven days ago, and 112 percent 14 days ago. The absolute numbers are pretty linear, but the relative growth rate in cases is actually slowing — +300 cases is a 33 percent increase on a 900 cases per day baseline, but a 20 percent increase on a 1,500 cases per day baseline. Since each infected person is capable of infecting multiple other people, this kind of trend is actually good news — we're no longer seeing the exponential growth that characterized the earlier days of the wave. |
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But you may notice that the two other metrics on that chart, new hospitalizations and positivity rate, haven't had the consistent slowdown that cases did over the past week or two. It's not like they've reversed course and started accelerating again, but their slowdown has been more gradual and more erratic.
If you line up our current wave's positivity rate next to past waves, one thing becomes immediately evident: this wave has gone on for a lot longer without peaking than the past three. |
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There are a few things that could be behind this. One could be just that we started from such a low caseload this time around that it's taking the virus longer to burn through a critical mass of susceptible hosts.
Note that the start point for the Spring 2020 wave is somewhat arbitrarily chosen because the data was so spotty back then. Positivity rate started really taking off after around March 28, 2020, the date I picked as Day 1 here — but confirmed cases in Minnesota date back at least three weeks before then. That first wave may be a better comparison for a wave that started from really low case levels and took a while to become generally circulating, though we can't really know exactly what was truly going on back in March of 2020.
Another explanation is that the delta wave is just different, that its increased contagiousness means it can take longer than past variants to burn through a population.
Missouri, a state that's been hit hard by the delta, didn't see cases start to fall until about 9 weeks after they first started to rise. If that holds true for Minnesota, we may be a week or two out from out own peak. |
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You might note one cause for alarm there: the sudden explosion of cases in South Dakota (and to a lesser extent, North Dakota) over the past few weeks. Infections can spread to neighboring areas; this surge in the Dakotas could lead to more cases in western Minnesota, and in turn to the rest of the state.
It's even possible this is already happening. Cases have shot upward in northwestern Minnesota lately (along with southeastern Minnesota, which doesn't have as obvious a geographic answer). Other western regions are also up. |
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The other interesting thing in that graph is the Twin Cities metro. For much of this wave, in July and the first part of August, the Twin Cities was accounting for a disproportionately high share of new cases. That's not the case any more. Growth there has flattened out in recent weeks while it continues to rise elsewhere.
It's possible that what we have happening here is not one Minnesota wave but several ones, including an early wave in the Twin Cities. This could explain the early explosive growth we saw in cases among Black Minnesotans (most of whom live in the metro). If so, it could be that that early wave is now peaking, but other demographic groups are now starting to get hit. I should note it's too early to say for sure if this is what's happening — this is just a hypothesis. |
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Meanwhile, my personal favorite chart for tracking COVID-19 is more encouraging. In it, I compare how fast case counts rise compared to test counts. Tests are still growing more quickly, as they have since April. But starting around July 1, when this wave kicked off, case growth has been accelerating vis-à-vis test growth.
Until now! Over the past week or so, this line has leveled off. In the past, that's been associated with imminent peaks. We'll see what happens this time. |
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So when will we peak?
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My previous prediction of an Aug. 18 peak was clearly wrong, and not just by a couple of days.
Two key moments changed the trajectory we were on earlier this month. First, after about Aug. 11, the rate of improvement drastically slowed. Second, this Tuesday's report (with data from over the past weekend) reversed the trend entirely, with a day-over-day acceleration that we haven't yet recovered from.
If you just project this all out from a month ago, you get a projected peak date of Aug. 31, next Tuesday. Now, I wouldn't put much — or any — stock in this, because that includes periods of steep improvement and slower improvement, and the slow improvement is the more recent one.
But next Tuesday isn't a terrible pick for a peak for other reasons. Basically, I'm calculating a "peak" by when the average positivity rate is lower than it was two weeks ago. By this very particular definition, that means our average positivity rate on Tuesday needs to be below 5.2 percent — very reachable from our current level of 5.4 percent. |
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| Now, a peak by this definition is one thing — a particular threshold I picked so I'd have something concrete to calculate. In a more general sense, a "peak" is when positivity rate starts going down consistently. Crossing the "0%" line above is no guarantee that positivity will keep going down — we could be due for an extended plateau, for example. We could even see it start rising again, though this hasn't happened in any serious, prolonged way in any of our past waves. |
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Below, I'll explore a few more stats about Minnesota's COVID-19 outbreak. If you want to learn more, I also recommend these other articles:
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| Hospital occupancy nears spring peak | | New hospital admissions have been rising pretty linearly for weeks now, though they're still below the peaks we saw in the last three waves. |
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| That's led to similar rises in the number of beds used by COVID-19 patients. These rates are just below the peaks we saw this spring, and still rising. | | |
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Vaccinations declining again after August bump
| | The danger of the delta variant combined with various incentives, outreach efforts and employer mandates led more Minnesotans to get vaccinated over the past month — but that bump is already receding. |
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That recent increase in final doses is mostly just the natural echo of the uptick in first doses that began a month ago.
As a result of this uptick, Minnesota recorded an increase in month-over-month vaccinations for the first time since April. But the total remains much lower than the spring vaccination peak, even as a share of the dwindling number of unvaccinated Minnesotans. |
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What's happening next?
| I'll keep updating you on if Minnesota's wave has peaked, or gotten worse!
Thanks for subscribing to this newsletter and for all of you who've sent me your feedback. As always, if you like this newsletter, please share it and the sign-up link with others who you think might enjoy it.
— David |
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