The epidemiology of covid in Ontario is very dynamic right now, both in terms of actual disease and in terms of testing. We need to consider both to understand what is happening.

The plot below shows cases per 100,000, tests per 100 k and positivity per test, by 10 year age bands.

These are by report dates, which is a common field in the test and case datasets.

What you can see is that there’s been a marked surge in cases in the 20-29 age group since mid-late August, both based on case counts and per test positivity. Per test positivity in this group has been at or above 4% for over a week now.

While incidence is rising in children under 10, and we might blame that on schools, what you can see is that the per test positivity in little kids is stable or even declining. So this “rising incidence” reflects testing requirements for kids related to schools.

Small children are now the most tested group, per capita, in the province. They’re being tested at 2-4 x the rate of other age groups.

We know that symptoms in kids are very poorly predictive of covid infection, so in that sense I wonder whether per test positivity in little kids is almost an index of prevalence in that age group...but I digress.

In terms of population health and the future demand for hospital beds, the important trend to watch relates to percolation of infection out of the 20-29 bracket and into older age groups. If we focus on per test pos, we see that that is happening in a rather dramatic fashion

You can see in the inset that per test pos in those 40 and over (and that includes over 70) has been dragged up over the past 2 weeks, and is now at or above 2%.

On a heat map, this becomes the typical “wedge” pattern that we have now seen over and over again, with percolation outward from the young adult group into older groups.

This is a bad sign. You don’t need to take my word for it. You’ll see this hit the hospitalization, and then icu, numbers in the weeks ahead.

We have seen this same pattern played out in Florida, France, Spain, etc. The trap is that if you want this NOT to happen here, you need to intervene proactively, before the crisis.

That means you need leadership that understands these patterns, and has the political courage to act when things don’t yet look horrible.

You can LOOK like a hero by taking aggressive action when people are dying in large numbers. It’s harder to BE a hero by acting as you know you should, and averting that crisis in the first place.

I am going to go do some work and hope that one of my excellent ID colleagues might take the reins here and explain why the CMOH’s comments on “30% false positives” were so incorrect, misguided, and destructive.

As you might imagine, there is some animated discussion happening right now in the DMs.

And to @bruce_arthur , the @metromorning appearance today is #8.

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