Texas, 3 Weeks Later

I started posting about COVID-19 in Texas about 3 weeks ago. Back then, the number of daily COVID-19 cases had started to increase dramatically, but the number of deaths had not increased. Let's have another look, this time with 3 weeks newer data:

The graph shows the number of new COVID-19 cases and deaths over the previous seven days. The scale of the two separate y axes (left axis for cases in blue, right axis for deaths in red) is chosen so that the two curves have the same slopes, for the most recent data, as indicated by the parallel orange lines.

The graph clearly shows that Texas had a three week delay between confirmed cases and the resulting deaths. Multiple studies have shown that this is close to the typical time between the onset of COVID-19 symptoms and deaths from COVID-19. Of course, there is some variation from case to case, with some people dying within a couple of days after diagnosis, and others dying after a couple of months in the hospital; but three weeks is about the average.

The delay between the curves also depends on when exactly a test is done; how long it takes to get and report test results; and how long it takes to report COVID-19 deaths. If we see a three week delay, that means tests are done (on average) shortly after first symptoms appear, and that the delay to get and report test results is roughly similar to the delay in the reporting of deaths - a few days. During the height of the epidemic in New York, tests were scarce, so most people could get tested only after symptoms had become severe. Furthermore, testing was backlogged so that getting results often took a week or even longer. Together, this caused the delay between increases in cases and the corresponding deaths to be much shorter, only about one week.

Unfortunately, the longer delay between case reports and COVID-19 deaths that we see now in Texas and many other states have caused many to believe that COVID-19 has somehow become a lot less dangerous - maybe even because the virus has mutated. This is not the case! While some progress has been made in treating severe cases, for example by limiting and better managing intubations, and by using drugs like remdesivir and dexamethasone, the effect of these improvements is much smaller than the apparent effect of the "death delay" and better testing.

Most people looking at the curves above will immediately understand that the number of weekly deaths had not reached its maximum yet. Even if new COVID-19 cases would remain at the current level or drop, the three week delay means that the number of deaths will continue to rise for another three weeks. During that time, the number of COVID-19 deaths per week in Texas will roughly double, to about 1,500 deaths per week, or 200 deaths per day. This number may climb even higher if hospitals are overloaded with the large number of COVID-19 patients, which seems to be happening.

We can use the knowledge about the delay between new cases and COVID-19 deaths to calculate "time-adjusted" case fatality rates for Texas. For example, Texas reported 69,491 new COVID-19 cases in the two weeks from 6/17 to 6/30/2020. With the average delay of 3 weeks, most corresponding deaths are expected to occur between 7/8 and 7/21. The number of reported COVID-19 deaths in Texas during this time was 1,421. This gives a fatality rate ("time-adjusted CFR") of 2%.

This means that if Texas announces 10,000 new COVID-19 cases on a given day, this will result in about 200 COVID-19 deaths, which will be reported roughly 3 weeks later. Actual reported numbers vary a lot from day to day, so it's better to look at weekly numbers: the current rate of about 70,000 cases per week will translate to about reported 1,400 COVID-19 deaths per week in Texas in three weeks. If Texas would keep the number of new transmissions constant, at about 10,000 reported cases per day, this would mean about 70,000 reported deaths from COVID-19 in Texas over the next year. As I explained in a recent post, it will take at least this long, and possibly more than two years, to reach "herd immunity" in Texas.

But if we look at the actual number of deaths in Texas, and compare them to the same weeks in 2019, and even grimmer picture emerges:

The table above shows the number of deaths from "natural causes" and the number of deaths from COVID-19 that Texas has reported to the CDC; the data are available for download on the CDC website.  I have used the most recent data (updated today, 7/22/2020), and omitted the last two weeks of data because the reporting for the most recent weeks is very incomplete.

As the table shows, that there were almost 6,000 more deaths from natural causes in Texas between the middle of March to the end of June than during the same period last year. Only about half of these "excess deaths" listed COVID-19 as a cause on the death certificate. In many US states, COVID-19 will only be listed if COVID-19 test was done before deaths, and if it was positive. For anyone who did not have a COVID-19 test before death, or who had a false negative test result, it is very unlikely that COVID-19 would be listed as a cause of death.

For every officially reported COVID-19 deaths in Texas until the end of June, there was another "excess" death that probably also was linked to COVID-19, either directly (an unconfirmed case) or indirectly. If this trend would continue, and the number of cases would remain at 10,000 per day, then the expected number of additional deaths in Texas over the next year would be 140,000. Given that Texas reported 187,806 deaths from natural causes in 2019, this would mean that the death rate in Texas would almost double.