COVID-19 Tests Falling Behind in the US

Bad news: it looks like testing in the US cannot keep up with the new cases.

Confirmed new and total cases vs. tests per day

When I looked at today's case numbers before going to bad, I first was glad - can you see why?

The number of new confirmed cases for the day was larger than yesterday - but just a bit! Maybe this was a sign things were slowing down! I should have gone to bed happy right there.

But it occurred to me that I should also check the number of tests done in the US. Here are the numbers from COVID tracking project:

If you look at the last column, you'll see that the number of tests per day has been pretty stable at around 100,000 tests per day. But confirmed cases are increasing rapidly, and the percentage of positive tests is slowly creeping up.

Ideally, test capacity should increase quickly enough to allow more people to get a test, for example those with mild symptoms, or anyone who had contact with an infected person. If that would happen, the percentage of positive tests should go down. But is has gone up instead: from about 15% ten days ago to about 20% in the last two days. There are only two possible explanations for this: either the criteria for who can get a test have gotten more stringent, or the percentage of people who are infected with COVID-19 has gone up significantly.

Some politicians have applauded the recent approval of a new test platform from Abbott as a great breakthrough in testing. They pointed out that the machine can get results in only 15 minutes; but somehow, they forgot to mention that the machine can do only one test at a time, so perhaps 4 tests per hour. The alternative technique of RT-PCR is usually done in batches of 96. But's it is a great thing for Abbott: the machines cost thousands of dollars a piece, and the tests cost about $45 each, compared to about $15 for other tests. Don't get me wrong, the Abbott machines can be great at certain spots were a quick result is essential. But they were developed for doctor's offices or single tests, and it is unlikely that it will remove the bottlenecks in COVID-19 testing.

Of course, the limited number of tests that can be done (relative to the current size of the epidemic in the US) also limits the number of new cases that can be detected. That gives the impression that the growth of the epidemic has slowed down - but it is likely that this is a false impression. Without increases in testing capacity that are faster than the growth in infections, we can not know for sure.

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Added 3/31/2020: The Republican governor of Maryland, Larry Hogan, stated in an interview today: 

"No state has enough testing."