Thread by @MarcelHarmon1

Whether or not the results of the 779 tests between 9/7 & 9/13 are a representative sample of the student body depend on sampling procedures & data analysis techniques we're not privy to. Though given that KU's testing at this point seems... 1/

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www2.ljworld.com/news/ku/2020/s…

driven more by limitations in it's ability to do more testing as well as laboratory limitations in processing the results, then it's likely this isn't statistically representative. The 10.9% positivity rate may underestimate the % of students infected between 9/7 & 9/13. 2/ #ksed

Unless the testing by Watkins was designed to specifically provide a representative sample, it's test results likely overestimate student body infection rates. These are students coming in w/ specific symptoms or other concerns. So the infection rate between 9/7 &... 3/

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9/13 likely falls somewhere between 10.9% & 26.7%, but probably much closer to 10.9%. Though others more familiar w/ KU's testing or epidemiology in general can provide corrections to this simple assessment.

Let's assume an infection rate of 10% among the student... 4/

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body between 9/7 & 9/13 & look at what this means in a classroom setting. Let's say we have a collaborative space/classroom w/ a capacity of 30 students (classrooms.ku.edu/rooms/st-f/221). According to KU this should indicate a room size of at least 600 sq. ft.,... 5/

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w/ an 11 ft. ceiling (classrooms.ku.edu/general-charac…). Though let's assume a 1,000 sq. ft. classroom.

KU has taken physical distancing into account (coronavirus.ku.edu/sites/coronavi…) so let's assume a class size of 16 students. This means at least 1 student in this class was... 6/

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potentially infected between 9/7 & 9/13. Based on KU's statement that building level filtration was generally not increased (protect.ku.edu/faqs#main-cont…), I'll assume a MERV 7 filter rating. While this same statement acknowledges the importance of fresh air, it says... 7/

nothing about KU's ability to increase ventilation rates by building/space, or if they did make any increases, how much they were able to do so. Depending on the specific system type & age, it would not be unusual for such increases to be limited or even impossible. 8/

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So let's assume a ventilation rate at 75% of ASHRAE 62.1's recommendation, which gives us 315 cfm for this classroom. I'll assume a recirculation air change rate of 2.0 ACH and an RH of 30%.

I'll assume an interactive class (speaking) & everyone is wearing masks,... 9/

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though let's say some students aren't as effective at keeping them up above their noses as others. So I'll account for that by saying only 75% are wearing masks.

After a 1 hour class, this calcs to an approximate 3.1% probability of infection for SARS-CoV-2 (<1... 10/

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additional person potentially infected after 1 hr). After 2 hrs, it's approximately 6.1% (<1 additional person potentially infected after 2 hrs).

If 2 people are initially infected, then the #s are - 1 hr: 6.0% / <1; 2 hrs: 11.7% / <2. This assumes no high shedders. 11/

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If no one was wearing masks, then the numbers for 1 infected person would be - 1 hr: 4.6% / <1; 2 hrs: 9.0% / <2.

For 2 infected people, those numbers would be - 1 hr: 9.0% / <2; 2 hrs: 17.2% / <3.

If we could hypothetically double the ventilation rate (& back... 12/

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to wearing masks), then the numbers for 1 infected person would be - 1 hr: 2.0% / <1; 2 hrs: 3.9% / <1.

For 2 infected people, those numbers would be - 1 hr: 3.9% / <1; 2 hrs: 7.7% / <2.

Let's go back to the original ventilation & see what the numbers would be at... 13/

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30 students - 1 hr: 3.1% / <1; 2 hrs: 6.1% / <2.

For 2 infected people, those numbers would be - 1 hr: 6.0% / <2; 2 hrs: 11.7% / <4. Reducing the number of students/class reduces the potential number that could be infected.

Obviously a lot of assumptions here. But... 14/

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it shows the importance of mask wearing, reducing class size, upping ventilation, & keeping infections rates low among students to begin w/. For KU, we don't know what's generally been done regarding ventilation, nor are we certain what student infections rates are. 15/

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