Thread by @nataliexdean

THINK LIKE AN EPIDEMIOLOGIST:
The chart below is tests per 1000 people. Relative to other countries, the United States is doing a lot of testing. So why do public health experts say that testing is inadequate in the US?
A thread. 1/7
Source: ourworldindata.org/coronavirus-te…

First, the amount of testing a country needs is not fixed, but rather it depends on the size of that country's outbreak. South Korea does not need to do the same amount of testing as the United States because our outbreak is much bigger than theirs. 2/7

For starters, we need enough testing to meet demand, and demand will depend on how many people are sick with COVID-like symptoms or have been exposed to an infected person. With hot spots everywhere, there is much more demand in the US. 3/7

In addition, for the same amount of testing, many more of our tests come back positive. This is reflected in higher test positivity (>5%). High test positivity implies that we need more testing to uncover more of the infections that are being missed. 4/7

Here we see daily tests per million (y-axis) against confirmed cases per million (x-axis). Countries at the same height are doing a similar amount of testing, but the US is far off on the right with a larger outbreak and higher positivity. 5/7
Source: ourworldindata.org/coronavirus-te…

The other major reason that public health experts are concerned about testing? Long turnaround times! These tests get counted in the official statistics whether it took 1 day or 14 days to get the results. But only the quick turnaround times are useful for control efforts. 6/7

So while we may be doing a lot of testing on a per capita basis, it is still not adequate because:
- Our outbreak is very large
- Our test positivity is too high
- Out test turnaround times are too slow
7/END