The Missing COVID metric

School District 214 now has a number of return-to-school metrics posted on its website.  In a Google document, they now track the weekly cases per 100,000 for our local area.  Separately, they track the student and teacher infection rates.

As of October 22 (as retrieved on October 25), the student infection rate stood at 0.08% and the staff infection rate, at 0.44%.  These metrics measure the number of students/staff testing positive over the past 14 days, as a percentage of the total student body and staff in attendance.

At the same time, as of October 24, the total cases for our local geographical area stood at 216.9 per 100,000.  On October 17, the total cases for that prior week were 110.3.

That is a dramatic jump, to be sure.  To do some basic math, that says that the percent of residents in our area who tested positive in the last 14 days, comes out to 0.327%, and this simple math says that school staff are becoming infected at a higher rate than the population as a whole.

But is that truly apples to apples?

It depends on what the infection rate is specifically for the working age population, and that rate is not easily accessible.

Here is a simplified attempt to derive this number:

According to the Statistical Atlas, 51% of the population of Arlington Heights falls into the “working age” groups — ages 20 – 60.

At the same time, based on some personal tracking of the Illinois DPH case counts by age, 72% of the cases occurred among people in that age range, for zip code 60005 and for the past month, approximately.  This means that working-age people are more likely to be infected; according to this math, 0.46% of the working age population tested positive for COVID within the last two weeks.

In other words, staff at District 214 are, at this point in time and based on this simplified calculation, at no greater risk of COVID infection than the population as a whole.

But this calculate is crude.  Due to the limitations of public data sources, I am unable to calculate this rate — two week positive tests specifically for working-age adults in the entire D214 geographic area, relative to the total working-age population.  (Of note, the IDPH website only shows cumulative cases; if you track individually, it’s necessary to re-access the site on a regular basis.)  But the district has access to greater resources and staff time.

Hence, the missing COVID metric that’s crucial for identifying how safe it is to initiate/maintain a given level of school opening is this:  how does the staff infection rate compare to the infection rate for the working population in the area?

 

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