Interesting COVID-19 Chart – Comparing County Results with State Testing Rates

The chart below looks complicated, but don’t let the looks deceive you. Here’s Pima and Maricopa Counties cumulative Cases per 1000 people (and the trend lines) compared to the number of daily tests in the state (it’s trend line is the orange, dotted U-shaped line.

  1. You can see the weird bump around 9/20 or so on the Pima County line. That is the first few days U of A tested out their homegrown antigen test on lots of students. The bump represents the excessive false positives in the test (they fixed it, I think). Remember, just because you test positive for something doesn’t mean you have it!
  2. The U trend on the tests is really interesting to me. Even as the summer wave was accelerating (far left) we see the trend in tests decreasing. Then when the cases are largely flat we see the trend reverse and start increasing. This could be some sort of psychological effect or maybe the number of tests is some sort of a leading indicator of case rates? This seems like an informative chart, so I’ll post it every week or two.
  3. Maricopa’s normalized case rate is around 7 cases per 1000 persons higher than Pima County. This has been sustained since mid-May. Not sure what it reflects, but it could be the greater adherence to government mandates (mask, distancing). Or it could have some demographic cause? It does seem that activity/going to work results in infections, because the normalized infection rates (per 1000 persons) are identical across the whole “working-aged” 20 to 64 age range. The 65+ population has just over 1/2 the rate per 1000 of the working-age group and the under 20 population has just over 1/3 of the rate per 1000 of the working age group (see second chart below).

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