For those wondering why the COVID-19 positivity rate in Alberta jumped so suddenly today, especially in the Central Zone, here's a quick explanation in a short (I promise!) thread...
If you look closely at the individual case data released today (shown here filtered in an Excel spreadsheet), you'll notice something a little funky.
There are dozens of cases dated March 29 among men in their 20s to 40s in the Central Zone, all listed as "recovered"...
It usually takes 14 days for a case to go from being considered "active" to "recovered," so the uniformity of this unusual batch of "recovered" cases — dated yesterday — suggests it was late-arriving data from a group setting of mostly men.
Alberta Health confirms this...
These are test results that came in a big batch, with a lag, from a prison.
Specifically, Alberta Health says: "It is due to an influx of tests entered into the system, primarily at the Drumheller Institution, which is a federal institution."
So hopefully that helps explain.
(It's also a good example of why, when you see something unusual in a dataset, there's often some kind of quirk in the data gathering or reporting process that might be driving it.)
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