COVID-19 May 03, 2020

This will be a fairly short Sunday post. The usual figures are below. My friend pointed out that it might be possible to remove some of the signal from varying testing rates by normalizing the cases by the number of tests. Not sure I'm going to go down that rabbit hole for a variety of reasons, the primary reason being that this is just a temporary hobby and I do still have a day job. However, a quick, back-of-the-envelope calculation shows that to compare current numbers to those of mid-ish April, I should multiply today's numbers by about 63%. With 30,000 new cases, 63% would be about 18,750. And, if you look at the daily case graph, that's only a few thousand off from where the Gompertz curve predicts it should be. So, the number of tests can be important.  Deaths continue to follow the model.  I still consider deaths to be the most robust metric. I may need to make a minor adjustment mid-week as the model seems to overdoing the numbers ever so slightly.

COVID-19 May 02, 2020

New day, same data trends. The daily new cases are not dropping, but holding fairly constant if you smooth out the weekly oscillations. I've added a new linear trendline based on the last 7 days (Edit: changed from 10 days) worth of data. The slope of this line is 26,445 (Edit: changed from 28,501) new cases/day. That's effectively the 7-day (Edit: changed from 10-day) average. I'll keep an eye on that number to see if it changes substantially in one direction or the other. I'm still plotting the red Gompertz model, which is clearly no longer valid.

Deaths, on the other hand, remain consistent with the model. They are inconsistent with growing infections. We will know in the next week whether the daily death curve starts to move sideways in concert with infections, or whether it will decrease, as would be expected on the slow downward glide slope of a waning pandemic. Based on the public displays of idiocy I've seen reported in the press, I expect the deaths to start moving sideways. And then up again.

Edits: I decided to use a 7-day linear fit since the oscillation has a period of 7 days. A 10-day fit is likely to bias the result. The numbers above have been updated, and I've updated the cumulative case figure below.

COVID-19 May 01, 2020

And so another month begins.  Where will the month end?  Unlike April, where the trajectory was mostly predictable, May is likely to be much more uncertain.  New daily cases are not falling.  They have more or less leveled off with a very, very large weekly oscillation superimposed.  On the other hand, the death rate is falling, slowly, on average but also with a large weekly oscillation. 

For now, the infections and deaths are inconsistent unless the mortality rate is changing substantially over time. If the mortality rate is invariant, then deaths should track infections with a lag.  Will deaths start to level off over the next week?  If not, that suggests that the behavior of the infection data is due to changes in testing and reporting.  It means that that data becomes almost useless without substantial analysis to remove the spurious signal.  It means that, for now, the death rate will be one of the few easily accessible and analyzable data for tracking this pandemic. 

COVID-19 April 30, 2020

As each day passes, the meaningfulness of infection numbers seems to diminish.  The number of tests continues to ramp up and this strongly affects the statistics.  The more tests you conduct on symptomatic people or people that have likely been exposed to the virus, the greater number of positives you'd expect.  Is this why the number of new cases confirmed each day leveled off?  It may be possible to answer this question at some time in the future when a clever epidemiologist is able to sift through the chaos that is the states' testing programs, but I don't think it's possible to do this in real time anymore.  That's a real problem because the number of new cases each day should be an important metric for determining the effectiveness or consequence of policy.

There are other metrics.  The number of daily deaths remains an important number.  I've said the dead are almost always counted.  The use of "almost" is appropriate.  Some dead are not counted.  Or, rather, some dead are counted but not attributed to COVID.  Sometimes they are counted long after they've died.  And, based on the unconfirmed news coming out of Florida, sometimes the dead are intentionally miscounted.  Perhaps this metric will soon become as unreliable as the number of new cases.  After that, we may have little left but to monitor hospital load.

Below are today's graphs.  The number of new daily cases is not decreasing as would be expected.  That has caused the cumulative number of cases to continue to rise at a greater rate than would be expected.  It is not quite an exponential rise, but rather a near linear increase with time. Total deaths and daily deaths are still well behaved with respect to the model.

COVID-19 April 29, 2020

Just a short post today with the graphs.  Daily new cases have settled down a bit, but the trend over the last week still does not match with the prior trends.  Testing is really ramping up in many states and social distancing policies are in flux.  All of these can lead to a departure from the prior trend.  We'll just have to keep an eye on it.

Deaths continue to match with the model predictions.  If the behavior of infection rates is indeed changing, then that should start to show up in the death statistics.

COVID-19 April 28, 2020

After reaching the highest number of new infections just a few days ago, numbers have plummeted to the lowest they've been in nearly a month.  Yesterday's 22,000 new cases are just a little over where the model predicts they should be. The data variability makes no sense in terms of a natural system.  The behavior has to be due to some combination of reporting cycles over the period of a week combined with an overall increase in testing ability.  Superimposed on that is almost certainly a signal due to changes in the policies of individual states.  Depending on which data set you believe, we are about to cross or have just crossed 1,000,000 recorded cases.  This is an artificial number and the number of actual infections is almost certainly 10 or 20 times greater.

Daily deaths have also dipped to lows that have not been seen since early in the month.  The last two days have been substantially below the model trend, but I expect the numbers to rise, as they typically do through the weekdays.  Deaths should not be strongly tied to testing availability, but the data still suffers from reporting inconsistencies.  We have crossed the 50,000 dead mark.

COVID-19 April 27, 2020

The number of new cases dropped significantly yesterday.  This is usually the case for the weekend, which has historically been the low point of the weekly oscillation cycle.  The question for the coming week is whether the numbers will begin to take off again or whether the numbers will relax back to the model trend.  If the numbers increase again, it will be interesting to see whether they do so exponentially, which is shown by the orange curve I've added back since yesterday.  Perhaps we are starting to see the rise of the foolish states.

The number of daily deaths plummeted yesterday to one of the lowest values in weeks.  This is following the high point roughly a week ago.  If the weekly oscillation is still operating, the numbers should increase over the next few days.  The question for deaths is whether they will rise back towards the model trend.

What is interesting is that while daily new infections are climbing daily deaths are dropping.  The rise in new infections could be consistent with the increase in testing.  The number of deaths is independent of testing.  If deaths don't rise within the next week or so, that means that any continued rise in the number of infections is mostly the result of increased testing and not an actual surge in the pandemic. 

Overall, the quality of the data has become increasingly poor. The amplitude of the weekly oscillation has grown, the reporting criteria have changed from state to state, and the way that earlier cases just now discovered are added to the pile contaminates the data.  If the data collection and documentation protocol were rated by scientific standards it would be a fail minus.  It really just goes to show how poor (absent) the coordination and standards are at the federal level.