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What counties in the USA are testing, and which are not?

From the PolicyLab testing data from HHS, below is a plot of SARS-CoV-2 testing rate of each county per 100k residents, with hotter colors with fewer tests and greener colors with more tests (I apologize for the color scheme if you are colorblind). Thank you Vicky Tam!


A few things jump out: some states with recent surges (Florida, Louisiana, Alabama and California) are doing a relatively high level of testing (North Dakota too), while others (Texas, Oklahoma, Georgia, South Carolina, Tennessee, Missouri, Ohio) are doing quite low levels of testing. Maybe even alarmingly low levels of testing.


This low testing can indicate one of several things: (1) there is not much virus so not many people to test, (2) the reported cases are extreme undercounts, (3) people are changing testing practices, e.g. not being tested when asymptomatic, or (4) PCR testing is being replaced by antigen testing that is not being reported.


If testing positivity is high, then explanations (2) and (3) make the most sense, and if low then explanations (1) and (4) make the most sense. Explanation (1) makes sense for places like Maine, but clearly not for recently surging states.


This is an interesting phenomenon to watch moving forward as (1) President Trump has talked about how "reducing tests will reduce cases", (2) The CDC just changed testing recommendations to suggest asymptomatic people should NOT be tested even if exposed to an infected individual, apparently under the direction of President Trump, and (3) in many states antigen tests are increasing used as fast tests for active virus, but the CDC guidelines are vague on whether these should be reported as tests and cases, so they are frequently omitted from the data reported to the government, e.g. Texas. I may have a more detailed blog post coming up looking more deeply into some of these issues.


All of these factors suggest there may be reduced testing and reduced case reporting, which may make it difficult to follow the progression of the pandemic, which in turn will make it difficult for local municipalities to make informed decisions about tightening or loosening mitigation strategies or opening/closing schools.


We need transparency, coordination, and accountability in data reporting!!!


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6 Comments


Jeffrey Morris
Jeffrey Morris
Aug 29, 2020

The saliva tests are typically pcr tests

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That just made me think- I’ve been pleasantly surprised Travis County has not had higher numbers with UT students going back. But I’ve read they have a huge testing program that uses the saliva kits. So those are antigen screens if I’m correct and would not be reported in TX 🤦🏻‍♀️

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Jeffrey Morris
Jeffrey Morris
Aug 27, 2020

If there is a shortage of pcr supplies some might use antigen tests instead and those might not get reported as cases

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I assumed they would still test everyone new coming into the hospital- but at this point who knows??

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Jeffrey Morris
Jeffrey Morris
Aug 27, 2020

Agreed and hospitalizations could also not go up because positive test needed to count hospitalization as covid related

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