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How are COVID-19 cases counted? Are they all “real” cases?
How are COVID-19 cases counted? Are they all “real” cases?
ratings:
Length:
9 minutes
Released:
Jul 23, 2020
Format:
Podcast episode
Description
COVID-19 cases have increased significantly in recent weeks. In reaction to the rise in cases, numerous states and cities have rolled back their reopening plans. Masks are mandated across half of the country.
It would be reasonable to assume that the numbers define the count of people who've tested positive for SARS-CoV-2 infection. They include more than that count.
It would also be reasonable to assume that the United States counts COVID-19 cases like all other countries do. That isn't the case either.
The CDC Guidelines for Counting COVID-19 Cases
According to the CDC guidelines, the case and death counts we see as U.S. citizens include both confirmed cases and probable cases. States began adding probable cases to confirmed cases in mid-April, though not all states adopted this more liberal approach to counting right away.
Many other countries count only confirmed cases. Because we use a far more liberal method of counting, it appears that in the United States, COVID-19 is out of control. In reality, it's a difference in counting methods.
It's as though in other countries, they're only counting Dodge Rams, but in the United States, we're counting all trucks.
Here's how it works in the U.S. Again, we now count both confirmed cases and probable cases.
A confirmed case meets confirmatory laboratory evidence. You test positive with a standard COVID-19 test. As straightforward as that seems, even the standard PCR test is surrounded by controversy.
A probable case:
Meets clinical criteria and epidemiologic evidence, but does not include a positive test for COVID-19
Meets presumptive laboratory evidence and either clinical criteria or epidemiologic evidence, but no positive test for COVID-19
Meets vital records criteria with no positive test for COVID-19
I'll share some examples in a moment, but first need to provide the additional CDC definitions.
Clinical Criteria
The CDC clinical criteria for COVID-19 includes at least one of the following:
At least two of the following symptoms: fever (measured or subjective), chills, rigors, myalgia, headache, sore throat, new olfactory and taste disorder(s), or
At least one of the following symptoms: cough, shortness of breath, or difficulty breathing, or
Severe respiratory illness with at least one of the following:
Clinical or radiographic evidence of pneumonia, or
Acute respiratory distress syndrome (ARDS).
And...no alternative, more likely diagnosis.
Laboratory Criteria
Confirmatory laboratory evidence: Standard PCR test.
This is what we've known of as COVID tests all along. These should be straightforward enough. And you'd certainly expect them to be accurate. They're not.
It turns out, a number of initial tests were contaminated. How many? We don't know.
As a result, some people who were actually negative for the virus, tested positive. Contamination occurred in other countries as well.
Additional studies showed that other tests could lead to a number of false-positive test results, but nobody knows how common this is.
What that means is that some of the people who had COVID or flu-like symptoms, and tested positive for COVID-19, might have just had the flu.
To cloud things even more, some people are testing positive for COVID-19, even after no-showing for their test.
Presumptive laboratory evidence: Antigen or antibody testing that suggests someone could have had COVID-19 in the recent past.
Though it's logical to think that if you have COVID-19 antibodies, you had and have recovered from COVID-19, that's not necessarily true. Other coronaviruses can cause you to test positive for SARS-CoV-2 antibodies.
In addition, the tests themselves are far from accurate. So again, using these tests to count COVID-19 case or death numbers can lead to flawed data.
Epidemiologic Linkage
Here's where things get really questionable. The epidemiological requirements are as follows:
It would be reasonable to assume that the numbers define the count of people who've tested positive for SARS-CoV-2 infection. They include more than that count.
It would also be reasonable to assume that the United States counts COVID-19 cases like all other countries do. That isn't the case either.
The CDC Guidelines for Counting COVID-19 Cases
According to the CDC guidelines, the case and death counts we see as U.S. citizens include both confirmed cases and probable cases. States began adding probable cases to confirmed cases in mid-April, though not all states adopted this more liberal approach to counting right away.
Many other countries count only confirmed cases. Because we use a far more liberal method of counting, it appears that in the United States, COVID-19 is out of control. In reality, it's a difference in counting methods.
It's as though in other countries, they're only counting Dodge Rams, but in the United States, we're counting all trucks.
Here's how it works in the U.S. Again, we now count both confirmed cases and probable cases.
A confirmed case meets confirmatory laboratory evidence. You test positive with a standard COVID-19 test. As straightforward as that seems, even the standard PCR test is surrounded by controversy.
A probable case:
Meets clinical criteria and epidemiologic evidence, but does not include a positive test for COVID-19
Meets presumptive laboratory evidence and either clinical criteria or epidemiologic evidence, but no positive test for COVID-19
Meets vital records criteria with no positive test for COVID-19
I'll share some examples in a moment, but first need to provide the additional CDC definitions.
Clinical Criteria
The CDC clinical criteria for COVID-19 includes at least one of the following:
At least two of the following symptoms: fever (measured or subjective), chills, rigors, myalgia, headache, sore throat, new olfactory and taste disorder(s), or
At least one of the following symptoms: cough, shortness of breath, or difficulty breathing, or
Severe respiratory illness with at least one of the following:
Clinical or radiographic evidence of pneumonia, or
Acute respiratory distress syndrome (ARDS).
And...no alternative, more likely diagnosis.
Laboratory Criteria
Confirmatory laboratory evidence: Standard PCR test.
This is what we've known of as COVID tests all along. These should be straightforward enough. And you'd certainly expect them to be accurate. They're not.
It turns out, a number of initial tests were contaminated. How many? We don't know.
As a result, some people who were actually negative for the virus, tested positive. Contamination occurred in other countries as well.
Additional studies showed that other tests could lead to a number of false-positive test results, but nobody knows how common this is.
What that means is that some of the people who had COVID or flu-like symptoms, and tested positive for COVID-19, might have just had the flu.
To cloud things even more, some people are testing positive for COVID-19, even after no-showing for their test.
Presumptive laboratory evidence: Antigen or antibody testing that suggests someone could have had COVID-19 in the recent past.
Though it's logical to think that if you have COVID-19 antibodies, you had and have recovered from COVID-19, that's not necessarily true. Other coronaviruses can cause you to test positive for SARS-CoV-2 antibodies.
In addition, the tests themselves are far from accurate. So again, using these tests to count COVID-19 case or death numbers can lead to flawed data.
Epidemiologic Linkage
Here's where things get really questionable. The epidemiological requirements are as follows:
Released:
Jul 23, 2020
Format:
Podcast episode
Titles in the series (100)
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