COVID-19 April 02, 2020

Today's total infection rate graph, created from the tallies at the end of the day yesterday, continues to show a consistent trend with the new, slower rate of exponential growth that was established about 5 days ago.  I want to emphasize that these data are very likely influenced by poor reporting and testing.  For example, this recent article from CNN reports that there are up to 160,000 tests backlogged at a single lab.  I think it is likely that at least part of the flattening is real--the rate of new infections really has gone down.  Nearly 80% of the country is now under some kind of quarantine.  That is going to have an effect, and most of those policies have now been in effect long enough to show, even if there is a lag in testing and reporting.

What is troubling is that the daily rate of deaths, and therefore the total number of deaths, appears to be rising without much of a break in slope.  Note that the 10-day daily death rate in orange is just barely below the rate for all the data (blue).  In principle, deaths should be correlated with the number of cases, but with a time lag.  If the number of cases has slowed, why haven't deaths?  We'll have to keep an eye on total deaths and especially the death rate to see if it starts to flatten more.  If not, that suggests that the testing data is significantly biased and problematic.

Another concern is that with so much of the country already sequestered, why hasn't the rate of new infections begun to stabilize more quickly?  Or, stated another way, if we wish to reduce the rate of new infections further, it seems like it's going to take even more draconian measures to do so. Either that, or we are going to have to live with this semi-flattened curve for a loooonnnnnggggg time.  The curve is not going to flatten naturally until a significant portion of the population has been infected and become immune, or, possibly, until warmer weather begins to affect the stability of virions.  The latter idea is only a possibility.   No one is sure how the virus will respond under warmer conditions.

Finally, I'll point out that the population is not uniformly distributed across the country.  Much of the rapid growth we saw was due to New York.  Other cities could be next to experience this growth, and that could cause the curve to steepen again.  The social distancing policies that are in place across much of the country should help mitigate this risk, but it is still there.  Florida only recently put in place relatively weak orders that are going to take at least 10 days to have an effect.  The major cities in Florida could spike dramatically within that period of time and set the US curve as a whole along a steeper path in the same way that New York did.