President Nero wants you to know that the U.S. has conducted a bigly number of coronavirus tests, higher than he can count, and maybe even more tests than there were people at his inauguration! Anyway, the U.S. is still terrible at COVID testing, as the following chart from Vox reminds us:
As the accompanying article points out, this is completely mediocre. It is a little better than before, but it nonetheless underscores that we are not ready to go back to a new-normal. All the actual plans I’ve seen begin with the presumption of widespread testing. The U.S. is absolutely nowhere close to that.
Even worse, a recent piece in The Atlantic suggests that bad testing may be the reason it appears that the case rate is flattening out in the last few days. Basically, the percent positive rate in the U.S. is very high – around 20%. Responsible countries like the Netherlands and Germany are apparently in the 6 to 8 percent range. A high positivity rate apparently is a sign that we’re not catching a lot of cases (as the numerous testimonies of people who have all the symptoms but can’t get a test because they aren’t being admitted to a hospital strongly suggest); the number needs to be a lot lower to feel confident that one is finding most of them. There’s wide geographic variation; New York’s rate is over 40 percent, and New Jersey around 50. New York City has a staggering 55% positivity rate.
There are a lot of ways to interpret the plateau in cases we’ve been hearing about, and The Atlantic piece is careful to suggest caution in using this particular metric of positivity rate. But still, of the apparent plateau, you can worry about this:
“There are several ways to interpret this development. It might suggest, for instance, that the more than 3.2 million tests completed in the U.S. over the past two months have finally captured a good chunk of the people who are actually infected. While it’s clear that the country is not capturing every case, this decline in new positive cases might suggest the country has started to get the virus’s spread under control. But there is another way to interpret the decline in new cases: The growth in the number of new tests completed per day has also plateaued. Since April 1, the country has tested roughly 145,000 people every day with no steady upward trajectory. The growth in the number of new cases per day, and the growth in the number of new tests per day, are very tightly correlated. This tight correlation suggests that if the United States were testing more people, we would probably still be seeing an increase in the number of COVID-19 cases. And combined with the high test-positivity rate, it suggests that the reservoir of unknown, uncounted cases of COVID-19 across the country is still very large.”
In other words, we should hope this approach is wrong. Certainly the apparent plateau in hospitalizations and death rates in New York is encouraging, though even there, there is likely significant under-reporting that the state is catching up on.
I dug a little into the North Carolina data (here), and can’t decide whether it’s encouraging or not – because the number of tests conducted per day is all over the place. If you just look at the total number of tests and total number of cases, they appear to be diverging:
On the other hand, the overall positive rate is slowly creeping up – 5.04% on 3/27 to 7/71% today. Not a bad number, but not going in the right direction, either, despite the appearance on the graph. On the third hand, the number of tests per day is all over the place:
I think the (lack of) pattern is worth noting because, as far as I can tell, North Carolina has been handling the pandemic pretty well. Here’s the total number of cases; the y-axis is logarithmic to highlight that the rate of increase is slowing:
At least, as far as we know. Wouldn’t it be cool if we had a national government, one with a president and a functioning executive branch, to make sure that the states were actually supported in their testing? As I suggested a while ago, we know how many “COVID-19 cases” we have. We just don’t know what that means.
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