COVID-19 April 09, 2020

I'll be showing mostly plots with linear axes today, because that format brings out a lot of nice details that I'd like to discuss. 

First and foremost, I'd like to emphasize how much the curve has flattened for both the number of infections and for deaths.  The first figure below shows the cumulative number of infections.  For a long time, we were following a very steep exponential curve similar to the blue dotted line.  The data has now departed significantly from that exponential function.  The best-fit exponential function of all the data no longer does a good job, and that's a really good thing. Instead of hitting 1,000,000 total cases this week, as we would have had we stayed on that steep curve, we are at less than half that.  The three-day curve fit is also below the 10-day, which is indicative of further flattening.  I would caution, however, that some of the biased weekend data is still influencing these curve fits.


A similar story can be told in the plot of total deaths.  We have departed significantly from the initial steep exponential growth.  Whereas 100,000 deaths seemed to be coming within the next two weeks, the current trends suggest that grisly number is much farther off, if it will be attained at all.  Doubling time of deaths is still around 4 days, which is still very high, but it's better than doubling every two or three days.  Hopefully, the trend will continue.

The daily number of new infections has almost recovered from the very low spurious weekend reports.  It will be interesting to see if today's numbers and Friday's numbers make up the difference.  The offset in the daily rate is still obvious, and the rate is almost where it was before the weekend.  Note that this plot is the only one with a semi-log axis, so it may be hard to see the details.

The daily death rate (on a linear axis plot) clearly shows the effect of the weekend numbers.  There was a spurious drop followed by a slight over-correction the day before yesterday.  Yesterday's numbers settled to a value almost exactly as expected.  My guess is that today's numbers and Friday's reports will continue that trend followed by another weekend of bad data.