What Normal-ish Means, Especially for D.C. Schools

One point some asshole with a blog Twitter feed routinely makes is that, if we could lower the prevalence of COVID-19 in D.C. to lower levels, we could return to normal-ish activities. So what does that mean? What we want is for the number of daily new cases to be at one per 100,000 people–which in D.C. would be seven per day (0.007% one week prevalence). That’s the level at which even risky activities become reasonably safe, since you’re unlikely to encounter someone with the virus.

As Yogi Berra might have put it (had he been an epidemiologist), “You can’t get infected if you don’t come in contact with anyone who’s infected.” This is true, but also appears to be beyond the ken of too much of our commentariat and public officialdom. At this level of prevalence (1 per 100,000 per day), using gyms–without masksdidn’t lead to infections in Oslo, Norway over a two week period. Low prevalence is not foolproof–it is absolutely not a vaccine, but it does keep infections low enough, such that we can mount an effective test and trace response, as well as survive the occasional bouts of stupid behavior.

To put an infection rate of 1/100,000 in the context of schools, we can look at D.C.’s public schools (DCPS). In its entirely, DCPS staff, students, and teachers number close to 55,000 (note that this doesn’t include the charter school system which is about 90% the size of DCPS). To keep the math simple, we’ll round to 50,000 DCPSers, which is about seven percent of D.C.’s total population. So, if D.C. has 50 cases per week, and seven percent of those cases affect someone in DCPS, we would expect two cases per week, give or take.

Two key points here. First, we will never not have COVID-19 cases in DCPS, even at a really low prevalence; without a vaccine or a very rapid, on-site testing scheme*, a COVID-free school system isn’t happening. Second, we can manage a few cases per week in the schools. Most students and schools wouldn’t be have to be sent home or closed. We could ‘flood the zone’ with testing and tracing to find related cases** in and out of the school system. But seven to ten times that amount, which is where D.C. is right now in terms of prevalence, and we’re quite strained in our ability to test and trace (remember DCPS is only seven percent of the city; D.C. also needs to deal with 93% of people not in the DCPS system). Likewise, at the current prevalence, it’s possible one or more schools get hit hard, requiring shutting down the entire school. And of course, all of this assumes that there wouldn’t be some spread within schools, so these are probably low-end estimates of the weekly number of cases if schools were open.

With four to six weeks of rolling back hard, we could lower prevalence to the point where we could reopen schools and do some other things. Yes, we would have to wear masks, limit indoor densities and so on, but we could return to normal-ish activities.

This is why some asshole with a blog Twitter feed keeps writing “Anger is still the appropriate emotion.”

*Even a very rapid, on-site testing scheme, between false-negatives and timing issues, won’t be completely iron-clad. Would be a vast improvement though.

**To date, I haven’t heard of a single superspreading outbreak in D.C. (i.e., dozens), which tells me that D.C. isn’t going deep enough on the contact tracing (alternatively, the mode of transmission could be fundamentally altered, but extraordinary claims require, at the very least, some evidence).

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1 Response to What Normal-ish Means, Especially for D.C. Schools

  1. ProNewerDeal says:

    I am also worried about the schools worsening the Currently Infected Rate/weekly Prevalence Rate.

    It appears that in IL, schools are left out of the state gov’s “Restore IL” plan & left to local school district judgement. Wgntv dot com said 9% of K-12 students in IL are going back to regular onsite school, 32% a mix of remote/internet & onsite, with the remainder 59% remote/internet. I feel there already several newsstories/anecdotes (suburban Atlanta high school, U N Carolina, etc) that shows the danger of schools with the current 50+/100K (or even 8+/100K as you mention) weekly Prevalence Rate.

    Fundamentally if you put 500+ humans indoors for 7+ hours with a 50+/100K rate, that is fundamentally high risk activity. It is why NBA & NHL playoffs are being played without fans, & a high portion of voters are using mail voting.

    A noble human social cause does not change this situation, whether it is school or police violence protests (which were at least possibly less harmful being outdoors). Social Science is important, but Biology is more important than Social Science.

    “Anger is still the appropriate emotion.” Thank you Mike. 100% agree. It is incredibly frustrating to me the US PTB refuse basic policies like a 6 week lockdown with 6 week UBI, that are proven effective from other nations empirical track record in crushing the Prevalence Rate.

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