How Texas Beat COVID-19

Perhaps this post should go on my COVID-19 science blog, but it's more observational than scientific. It's also about Texas, and that's still the last place where I windsurfed, more than a month ago. Texas still reports a relatively low number of COVID-19 infections: 22,393 as of 4/23.

How did Texas keep COVID-19 case numbers down? Let's have a look at the COVID-19 case map:

Darker mean more cases. Interestingly, you can make out the boundaries of Texas' right neighbor, Louisina: things are darker in Louisina. Well, everyone knows that Louisiana had a lot of COVID-19 cases after Mardi Gras, right? That shows clearly on the map that shows cases per million inhabitants in a state:

There's an interactive version of this map where you can see case numbers here.

The interesting thing is that COVID-19 seems to stop at the state line between Louisiana and Texas. The counties on the Louisiana site are much darker, indicating much higher case numbers than the counties in Texas. Did we discover a "disinfecting effect of state lines"? Well, certain orange-blonde people might conclude that, but I highly doubt that's the answer.

One more map to look at: the number of COVID-19 tests done in each state (interactive version here):

Looks very similar. If you use the interactive version, you can see that Louisiana did almost 4x as many tests per 1000 inhabitants than Texas. "But they had to because they had more cases!", you say? Looking at the first chart, it is clear that it is the other way around: Texas reports fewer cases than Louisiana because it does fewer tests.

Perhaps this does not come as a surprise, considering that the lt. governor of Texas has stated that "there are more important things than living", and that "Texas should not be shut down because a small percentage of the population is dying". Just test fewer people for COVID-19, and you have fewer cases! You'll also have fewer COVID-19 deaths, because that requires a COVID-19 diagnosis. Genius!

Looking back at the map on top, you can see that it is also easy to make out to top (northern) border of Louisiana to Arkansas. That's another state that has not done many tests. Again, we see a sharp drop in infections right across the state line.

Without a doubt, Texas and Arkansas have lower reported COVID-19 numbers because they do less testing. For a quick comparison, let's look at New York: the state has done almost 700,000 tests, and has 263,460 confirmed cases: about 1.3% of the population is confirmed positive. But a couple of different studies have concluded that about ten times more people in NY have been exposed to the virus. Even with a lot of testing, the tests have under-estimated the number of infected people tenfold.

Now some "smart" people may conclude that this is "good news", because it means that COVID-19 is less deadly. Well, not really. Scientific studies had already concluded that the actual "infection fatality ratio" is about 0.4% to 1%, with 0.6% being a typical value. And that's roughly what we get for New York, too, when we assume 10-fold underreporting of cases.

So, what does that mean for Texas? Texas has 29 million inhabitants. If about two thirds of them would get infected, that's 20 million cases. With a fatality rate of 0.6%, that's 120,000 COVID-19 deaths for Texas alone. But with perhaps 1 in 20 cases getting tested, the official reported number of COVID-19 death in Texas can be kept down to 6,000 - less than New York! Eventually, some statistician may discover that the annual death rate for Texas increased by more than 50% during that time - but that will probably be years from now, since it takes a very long time for most death statistics to become publicly available.