COVID-19 May 18, 2020

I know it's tempting to look at individual daily numbers and make inferences about what is happening.  This is especially true if the daily number comports with your beliefs.  As a scientist, it's important to recognize and the short circuit the insidious nature of this confirmation bias.  As an example, the large number of new infections (1801) reported in Texas the day before received a lot of press, and many were quick to jump on that as evidence that there was a cause and effect relationship between that number and Texas's loose quarantine policies.  The number of new cases in Texas yesterday was 785.  That is one of the lowest numbers reported by Texas in the last two weeks.  Will that make the news?  Will those who jumped all over the 1801 number mention it?  The answer is probably no and no. 

It is generally unwise to focus on an individual daily number.  All the numbers must be taken together and understood in the context of the situation.  That situation includes an abysmal testing and reporting system that lacks nationwide standardization.  Daily numbers go up. Daily numbers go down.  I've taken to using a 7-day average because that seems to at least smooth out the weekly cycle that is inherent in the data.  The daily variations tell me that looking at the data with a fidelity shorter than about a week is probably bad data analysis.   If the numbers in Texas are going to respond to their policies, it will show up in the longer-term average.  It's not going to happen overnight, which means it's not going to show up suddenly as a big increase in just one day.  At least it's not likely to turn out that way.

And now, here are the usual plots:

COVID-19 May 17, 2020

Although I post the daily statistics each day, the interpretation of these data really comes down to two days each week: the day of the minimum and the day of the maximum.  If you look at the daily deaths below, you'll see that we hit the weekly peak a couple of days ago. It was much lower than the previous week, which is good because the previous peak was a record high.  And then the minimum value last week dropped it back below the Gompertz model curve.  This drop brought the average back closer to the model.  In the next few days, we'll see what this week's minimum will be.  Will it be lower than the value on May 10?  It looks like it will need to be 600 or below if the average is to maintain adherence to the Gompertz model.

In the meantime, the daily new cases continue the very slow linear downtrend.  Will that continue?  We had a peak a couple of days ago that was close to the previous week.  If this week's low isn't lower than last week then the downward trend will be broken and we will be either steady and increasing again.

More than a week ago I analyzed the increase in testing in comparison to the reported new cases.  Testing is still increasing and it is difficult to tease out what fraction of the trend in new cases is due to the testing.  The more you test, the more cases you expect to confirm, at least up to a point.  The fact that cases have been slowly decreasing could be considered a good sign.

So, the next couple of days will be filler while we await the minimum values for the week.

down to waiting to see where the weekly minimum and maximum end up.  Everything else is filler.

COVID-19 May 16, 2020

It's a pretty typical weekend from the standpoint of the numbers.  We're coming off the weekly peak values for deaths and new cases.  I'm still watching the new case data closely, because we may be diverging from the very slow, average, steady decline of the last few weeks.  As I mentioned yesterday, this week's peak was close to the previous week.  If the upcoming week's minimum does not drop below last week's then we are likely to be entering a new phase of steady and possibly increasing cases once again.  That shouldn't be surprising given the lifting of strict stay at home orders.  It's a beautiful day here in Colorado.  I'm going to go enjoy the day.  I hope you all do the same, but please keep extreme social distance and wear your masks for our collective mutual benefit.

COVID-19 May 15, 2020

I usually try not to pay to much attention to the day-to-day variations but yesterday's report on new infections is interesting. If you look back over the past three weeks, you'll notice that the weekly peak was lower each week and the weekly minimum was also lower each week.  Yesterday, the daily new cases exceeded last week's peak.  Is this the start of a new trend?  I've been anticipating something like this since the States started re-opening, and it's about the right time between those policy changes and the emergence of symptoms from those infect about two weeks ago.  Stay tuned.

The death statistics are still in line with the model.  Deaths should lag the infections by two weeks or so, so the new cases should be a leading indicator of future deaths.  Stay tuned for that, too.

COVID-19 May 14, 2020

I noted that this week would be a key test for the Gompertz model as it related to the death statistics.  Based on yesterday's numbers, it looks like the model continues to hold reasonably well.  Today is usually when the peak number rolls in for the week.  Unless it is unexpectedly high, the 7-day average should match the model very well.  Note that the cumulative death statistics in the first plot mirror the Gompertz curve to very good accuracy.

The infection rate continues to do its thing with a slow downward trend.  Nothing really more to stay about it other than it is rather consistent once the weekly oscillation is averaged out.

COVID-19 May 13, 2020

As I typed the date into the header of this post I realized what a distorted sense of time I have now.  It's mid-May.  I haven't left the house since mid-March, except to walk the dog.  Two months.  How did that happen?  Over those two months, we've seen the rapid rise of the pandemic, a flattening of the curve, and now the persistent gnawing of a virus that isn't going to go away.  Collectively, our society and government aren't exactly helping either.  I find it interesting that after all the measures taken over the last month or two, we are still where we are today, as shown in the plots below.  In the US it seems that the last two months represent the best we can do.  Doing less, which is what's starting to happen across the country, means things are likely to get worse again. They are certainly unlikely to get better.  It's going to be a long summer. People are such selfish prigs.  Having to suffer the inconvenience of a mask for the benefit of your neighbor.  Oh, the humanity!  Mask. Dead person. Mask. Dead person.  Which to choose?????!!!!!!

COVID-19 May 12, 2020

The trends continue as they have for at least the last two weeks.  New cases are decreasing very slowly on average.  The 7-day average last week was about 27,000 new cases/day.  Today it's close to 24,000.  That still means well over 100,000 new cases each week.

The death statistics are also following their established pattern. Yesterday was the low point in the weekly oscillation.  The question for later this week is what the high will be and whether that takes it substantially off the Gompertz curve.  Note that yesterday's low was about the same as the previous week whereas the Gompertz model demands that it continue downward.  Since the daily new cases have flattened it should not be surprising the daily deaths start to do the same, but with a time lag.  I suspect this is the week when the death statistics fall off the Gompertz train. If that happens, it means the projection for 100,000 dead that has held for weeks will be a minimum.