COVID-19 Arizona University Area Outbreaks

Below you’ll see the Arizona Zip Code map of Case growth in the last week. Color of the bubbles represents the % growth in cases over one week. Size of the bubble represents population size of the zip code. What do we see?

1. We see two zip codes with growth far greater than any others. 85719 (U of Arizona) and 85281 (ASU) come in at 38% and 23% growth in cases over the last week. The next highest zip code is in Buckeye and comes in at 7.3% growth.

2. Flagstaff comes in around 4.3% growth. Perhaps they party less at NAU, or maybe there are less cases at altitude?

3. The below map only shows the top 30 zip codes. Most of these are under 5% growth.

4. Right now I’m doing this to see if the university cases spread outside the university areas. My hypothesis is that they will remain contained and the infection will burn itself out in those zip codes. I’ll be watching this and publishing results about every week. I’m also watching the hospital stats closely to see if the university case growth will result in increases in hospitalization.

Arizona map of top 30 zip codes by case growth between 8/30 and 9/5/2020
Table showing top 18 zip codes by case growth between 8/30 and 9/5 and some info about each zip code


Apparently, it turns out that some of the numbers from the Antigen tests have been false positives. The U of A admitted this and in doing so, it became clear that positive Antigen tests are going to the university health center to take PCR tests to confirm. Initially, the state was counting all of the Antigen positive tests as positives overall, but that seems to have stopped. Recall my earlier discussions about specificity and false positives. Any time a test has a specificity of around 97 or 98% and the disease is infecting only about 2-3% of the population you’re going to have about 1/2 false positives. See the university’s chart below. If my detective work is correct, all 109 Campus Health tests below were on people who had come up positive in previous days/weeks on the Antigen test. If true, then there’s about a 60% false positive rate (which makes sense based upon the possible specificity of the Antigen test and the rate of infection on campus). Will keep watching this, but it seems less concerning than before.

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