Updated: Jan 3, 2021
By Jerald Hughes
& Scott Robinson
The third wave of COVID-19 infections began on September 13, 2020. On that day the 7-day average of new cases began to rise again, making a total of 112 days since then. These numbers increased only very gradually, but starting about October 8, 87 days ago, the curve began bending upwards more sharply, as exponential spread took hold.
Chart: Daily Cases, 3rd Wave
There have been two data disruptions during this time: from first, the Thanksgiving holiday, and then the combined Christmas and New Years holidays. January 2, the most recent number in this analysis, presented a huge single-day number: 277,897. Since January 2 begins the normal weekend dip, we are not actually out of the fog of data disruptions yet; the soonest day we could expect that is January 5, the Tuesday after the weekend. It is very likely that this record-high number includes cases whose reporting was delayed; however, it also likely contains new cases caused by spreading events which occurred as a result of holiday travels and gatherings. The daily deaths show the same progression, lagged by about 18 days.
Chart: Daily Deaths, 3rd Wave
In both measures, there are recent very high numbers. On December 30, the daily deaths data at covidtracking.com recorded by far the highest number yet seen, 3903. In both measures, we also see that the most recent spikes have bent the curves upwards again, already regaining most of the ground lost because of the data disruptions of the holidays.
The hospitalizations data show a much more consistent picture of steady increase. The 7-day average of the daily hospitalization numbers shows no interruptions at all in the climbing numbers of severely ill patients.
Chart: Hospitalizations, 3rd Wave
Since the third wave of infections has been re-ignited twice by holiday spreading events*, there is no simple way to predict how long the currently observed surge will continue before leveling off and then decreasing for good. However, one indicator that at least gives a direction of future changes is the positivity rate. The data in the following chart was computed by dividing the 7-day average of daily cases by the 7-day average of total daily tests given.
Chart: Positivity Rate, 3rd Wave
As of January 2, the positivity rate has been increasing. It was already at high levels, above 10%, and in the most recent number shot up over 13%. This is a very bad indicator, and signals that we should not expect a quick recovery from the current surge.
* Per original projections, the third wave should have tapered off on or around Day 77.
All opinions expressed in this blog are solely those of the authors, and do not reflect those of University of Texas Rio Grande Valley, or any organizations of which either is a member.