COVID-19 April 07, 2020 Special Colorado Edition

With today's numbers hot off the press, the range of possible Gompertz model outcomes has narrowed.  Baring some strange event, I feel reasonably confident with the Colorado predictions.  What does "reasonably confident" mean?  I think they are upper limits and the actual numbers will not be more than about 30% higher at most, probably lower. Maybe I'll eat some crow later. We'll see.  Maybe I'll eat some crow later.  We'll see.

So what do the numbers say?  The Gompertz model (see previous posts about this model) predicts 20,000 total infections.  The number of new daily cases will peak at 441 on April 11. Colorado will reach 10,000 cases--halfway to the final number--on April 18.  Final deaths will be 800.  The peak number of daily deaths will be 18 on April 15.  Colorado will reach 400 deaths--halfway to the final number--on April 21.

What's interesting about these predictions is that the Gompertz growth rate for both infections and deaths is the same: 0.06.  Yet, the curve fits for both data sets were arrived at independently.  The fact that they have the same growth rate provides a good amount of confidence in the predictions.  Assuming that deaths are proportional to the number of infections, you'd expect to see the growth rate be about the same.  Furthermore, note that the peak in deaths and the halfway point for deaths lags the infection case milestones by about four days.  This delay between the official infection report and death is reasonable.  Thus, the two model results for infections and death are consistent.

COVID-19 April 06, 2020

Yesterday, I made a point of describing how screwed up the weekend data appears to be.  Several of you chimed in with anecdotal information that was in concurrence.  Thank you! 

I thought I'd follow up with a little bit more analysis and data.  I'll let you decide.  Below is a plot of the number of new infections each day.  The reported data is in blue.  The orange data represents predicted numbers based on a Gompertz model.  I've plotted this on a linear scale rather than the log scale I've typically been using.  The linear scale lets you see variations easier than a log scale.  See those last two points?  I've circled them in red. Those are the data that were reported on Sunday and Monday.  To my eye, the Sunday data is way, way out of family with every other data point up to that point.  The Monday data is a little better in that it is at least increasing again.  I've seen similar aberrations previously.  I've circled those in green.  The earlier times aren't as obvious as the ones this weekend, but that's because all the numbers were much smaller back then.  But, the blips are there.  There are similar patterns in many, but not all, of the 50 states.  Anyone want to lay odds that we'll see the same pattern next weekend?

It will be interesting to see if we get a flood of data coming in later this week to make up the difference.  It's possible (likely?) that agencies and labs are not working on the weekends or are at least running with minimal staff.  Let's also remember that testing is still not able to keep up with demand even when labs are going full bore.

In the meantime, what I believe to be spurious data is affecting the trends.  So, for now, those low numbers have slightly slowed the doubling rate.  I've seen a lot of press and reports stating how good the numbers were this weekend. I would exercise caution. Those numbers could be real.  Or not.