“I Was Wrong” on Reopening Ottawa

Roughly two weeks ago I wrote a post Against Reopening Ottawa. Since then, my predictions have turned out to be mostly wrong.

First, here’s same the chart I published at the time showing a moving average of new cases in Ottawa:

And now here’s the same chart updated as of the data available today from Ottawa Public Health:

At first glance I sort of feel vindicated, since I predicted cases would keep going up, and they definitely did. But pretty much all of the particulars of my predictions were wrong. In relation to Ottawa cases, my three predictions were:

  • Based on the original data I inferred a steady doubling time of two weeks; actual new cases went up way faster than that, and then flattened completely, and now seem to be decreasing again.
  • I predicted a brief slowdown in new cases starting around July 21st, due to Ottawa’s mandatory mask bylaw going into effect on July 7th. If you squint a little it kinda looks like that part might have been right, but on closer inspection it isn’t. The timing is off (the graph flattens well before masks would have an impact, and starts decreasing well after) and the sharp drop in new cases is so recent that it’s liable to disappear in the next few days anyway (Ottawa reports cases by first symptom where possible, so each new day’s data tends to backfill more cases over the last week or so).
  • I predicted that starting August 3rd or shortly after, cases would spike again due to stage 3 of reopening. This one isn’t right or wrong yet as we haven’t gotten there, but I’d no longer make the same prediction today.

I also made some less rigorous province-level predictions that turned out to be (mostly) wrong:

  • Ontario did see a brief more general increase in cases after my post, but that has stopped, and if you zoom out cases still seem to be trending clearly downward everywhere but Ottawa. I’ll give myself a win for predicting that Peel and other previous hot spots were mostly under control at that point, but Ottawa is now one of the regions with the most reported daily cases, making it an outlier, not a pack leader.
  • British Columbia cases have continued to pick up again, but apparently in the same ways as Ontario; they have one region that’s become a hot spot and everywhere else is well under control. The main difference is that BC’s infections are so low to begin with that their hot spot is swamping their general numbers and making it look like the whole province is in trouble.
  • Alberta I admit I don’t really understand. Their data seems to have done the same thing as Ottawa: a sharp increase followed by an immediate flattening. But they only have two major population centres (Edmonton and Calgary) and neither city on its own shows this pattern. If anybody has a better understanding, please leave a comment.

Finally, there’s a few other miscellaneous points I wanted to make:

  • As I mentioned parenthetically above, Ottawa reports cases by date of first symptom where possible (or even date of infection, if the source is known), which means that new cases reported on a given day are almost always backdated by a few days and up to two weeks. Thus we should expect the last week or so of numbers to show up as lower than they will be in the final tally. This is why I’m not convinced by the magnitude of the recent “dip” in new cases in my chart above, and explains why what was a gradual uptick in my previous post turned into a sudden spike. It does also vindicate me “reading too much into the graph”, although I didn’t realize this at the time so I can’t take credit for it.
  • Ottawa Public Health addressed the recent spike shortly after I published my last post, claiming that it was unrelated to reopening and more related to private parties and lack of distancing in private spaces (in particular among younger age groups). This seems like a generally plausible explanation, and I don’t have any better guesses that explain the weird shape of the data. There’s been so much garbage floating around from the WHO and the CDC, it’s nice to get evidence that my local health authorities actually know more than I do about COVID.

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