Trends in new COVID-19 cases don’t offer good news
George Lord
George Lord, Ph.D., is a sociologist who previously was a faculty member at the University of Memphis and dean at the University of the Virgin Islands. He retired in 2015 from the Mayor's Innovation Delivery Team in Memphis.
This week I have read several articles in The Daily Memphian which appear to be written to assuage my fears regarding the coronavirus. Geoff Calkins and Chris Herrington tell me things are getting better.
Calkins, the sports guru who brings humanity to our daily foibles, tells me to be happy and celebrate because the Shelby County Health Department has gone to twice-a-week news conferences instead of daily. This is because we have done such a great job with our response to all things virus-y.
Chris Herrington, a personal acquaintance whose basketball knowledge and insights I also enjoy immensely, tells me I just need to make good choices. I agree — hope and good choices are things we must take to heart.
But I just do not see many reasons to celebrate. I want to, believe me. I have been confining myself to home since March 14 except for my weekly drive to make my no-contact pickups at the grocery store and the ER visit (but that’s another story). I would love to be out and about in this great city!
The City of Memphis and Shelby County put out guidelines early on which conform to advice from the Centers for Disease Control. The guidance identified three primary conditions to be monitored in decision-making around moving forward in a phased reopening: 1) Number of new cases level or trending down for 14 days. 2) Hospital capacity. 3) Testing and tracing capacity. These three metrics, in addition to a lengthy list of additional indicators, would be monitored and used by the COVID-19 task force to begin easing restrictions when the cases are stable or trending down for 14-21 days.
Let’s take these guidelines in reverse order. The county has reached its goal of having capacity to test 2,400 individuals a day, which they have defined as adequate. Of course, this means it would take 270 days to test every resident in the county, not including retesting those with the positive tests to assure they have recovered.
We seem to be able to check off No. 2, given the availability of the new facility built in the old Commercial Appeal building with 401 designated COVID-19 beds. Lack of hospital capacity would definitely be a reason to delay reopening, but should adequate capacity indicate all is good? That’s a bit like rolling back enforcement of seat belt or drunk-driving laws because there is plenty of room for us at the hospital.
Before we talk about the first guideline, trends in new cases, let’s look at the ‘positivity rate,’ which seems to be prominently featured in reports of how well we are doing. In a briefing for nonprofits provided by the city on March 11, the decreasing positivity rate was cited as the primary metric that was driving the move toward reopening. What is the positivity rate? It is the number of new positive cases divided by the number of tests done. So, if the number of tests increases, you could see a rise in the number of new cases but a lower positivity rate. Since that is the case, it is important to understand who is getting tested and why.
If there is a scary story in the news about potential exposure at a local store, then maybe many people who went to that store will rush to get tested, regardless of whether they were actually exposed or not. New cases would surely be uncovered but the positivity rate might decrease. If, on the other hand, we were certain that most of those getting tested had been exposed to someone who was positive, maybe this metric would have more meaning. But right now, in this county, it isn’t really all that helpful.
So, back to what was supposed to be the primary metric to determine whether we are winning the COVID war — trends in the number of new cases. I started tracking the number of new cases, operating under the assumption that this metric is much more reliable and valid as an indicator of the community trend.
To move in to the first phase of reopening and the second phase of reopening, the number of new cases is supposed to be level or trending down for 14 days. A 21-day stable or downward trend would be even better, showing an ongoing decline in cases.
The numbers I track come from the county data provided here by the University of Tennessee Health Science Center. As you can see, there are not more than three days in a row where the count of new cases is lower than the count on the previous day. Granted, there is much fluctuation from day to day, but the trend overall has been upward. Clearly, there has not been a 14-day period when cases are level or decreasing.
Separately, I looked at the trend during Phase 1 and am currently tracking the trend during Phase 2 — both phases indicate increasing, not decreasing, numbers of new cases.
So, where is the good news to celebrate? New cases are increasing, which means the recent move to Phase 2 is likely to result in even more new cases as people return to their previous routines and relax precautions such as masks and maintaining distance. (Hopefully everyone will continue to wash their hands because that’s what they should have been doing all along.)
I hope I am wrong. I hope things are improving. However, the primary metric that was supposed to guide our decisions isn’t moving in the right direction. It wasn’t telling us what we wanted to hear, so it appears as if we’re choosing to ignore it. If there is a flaw in my data or reasoning, I hope someone can point it out to me. I too want to “return to normal.” I have blues to hear, ribs to eat and grandkids to hug.
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