Utilizing CDC estimates to review an article regarding Covid 19.
Let's start with a a little background reading from a June 25 CDC Telebriefing on Covid 19.
Maggie Fox, a reporter from CNN, is asks Dr. Redfield to explain a comment regarding the number of potential infections in the United States. Ms. Fox asks a good followup question, but Dr. Redfield's response has been largely ignored by the media and the politicians as make decisions regarding their response to COVID 19.
Maggie Fox: Thanks. Dr. Redfield, I was very intrigued by something you said, that for every case that’s tested positive, there might be ten that weren’t detected. Can you expand on that? And I think you probably know, the Wall Street Journal has said that the CDC estimates many millions more cases than has been diagnosed. Thanks.
Robert Redfield: Yeah. Thank you for the question. I mean. We have one of the realities, because this virus causes so much asymptomatic infection. And again, we don’t know the exact number. There’s ranges between 20%, as high as 80% in different groups. But clearly, it causes significant asymptomatic infection. The traditional approach of looking for symptomatic illness and diagnosing it obviously underestimated the total amount of infections. So, now, with the availability of serology, the ability to test for antibodies, CDC has established surveillance throughout the united states using a variety of different mechanisms for serology, and that information now is coming in and will continue as we look at the range, for example, where you have a different range of percent infections, say on the west coast, where it may be limited, say 1% or so, and then you have the northeast, where it may be much more common. The estimates that we have right now, that I mentioned — and again, this will continue with more and more surveillance — is that it’s about ten times more people have antibody in these jurisdictions that had documented infection. So that gives you an idea. What the ultimate number is going to be — is it 5-1, is it 10-1, is it 12-1? But I think a good rough estimate right now is 10-1. And I just wanted to highlight that, because at the beginning, we were seeing diagnosis in cases of individuals that presented in hospitals and emergency rooms and nursing homes. And we were selecting for symptomatic or higher-risk groups. There wasn’t a lot of testing that was done of younger-age symptomatic individuals. So, I think it’s important for us to realize that, that we probably recognized about 10% of the outbreak by the methods that were used to diagnose it between March, April, and May. And I think we are continuing to try to enhance surveillance systems for individuals that are asymptomatic to be able to start detecting that asymptomatic infection more in real time. (source: https://www.cdc.gov/media/releases/2020/t0625-COVID-19-update.html)
Now, we have this report on Fox2now.com out of Jeffereson City, MO. The purpose of the article/"report" is to answer the question: How do COVID deaths compare to other illnesses, like the flu or even the H1N1 pandemics of 1918 and 2009? It’s a common question.
Let's take a look at the "report."
According to the Missouri Department of Health and Senior Services, the state has recorded 63,797 cases of SARS-CoV-2—an increase of 1,267 positive cases from the day before—and 1,325 total deaths as of Thursday, August 13. That’s a case-fatality rate of 2.08 percent.
Notice how they calculate the case-fatality rate....first, they use the recorded confirmed cases and the number of deaths from the MO DHSS - notice that these are NOT ESTIMATES. Why would they ignore the statement from the head of the CDC that the number of infections that we are finding through testing likely only represent 10% of the cases?
Now, if we utilize the CDCs belief that we are finding 10% of the cases with our current methods of testing, we can then calculate the number of cases the CDC actually believes would be in Missouri.
So, we need to ask the question, 10% of what number is 63,797? To answer this question, we will divide 63,797 by 0.1. This gives us an estimated 637,970 infection cases in MO.
How does this new estimate affect the case fatality rate for MO. Comparing the number of reported deaths,1325, by our new estimated total, 637,970 gives us a case-fatality rate of 0.0021 for the state of Missouri.
The article then reports the national case-fatality rates for different flu seasons, the Spanish Flu, and the swine flu epidemic using data from the CDC. This allows the reader to the answer to the question the article is supposedly answering.
According to the Centers for Disease Control and Prevention (CDC), preliminary data on the 2018-2019 influenza season in the United States shows an estimated 35,520,883 cases and 34,157 deaths; that would mean a case-fatality rate of 0.09 percent. Case-fatality rates on previous seasons are as follows: 0.136 percent (2017-2018), 0.131 percent (2016-2017), 0.096 percent (2015-2016), and 0.17 percent (2014-2015).
The 1918 H1N1 epidemic, commonly referred to as the “Spanish Flu,” is estimated to have infected 29.4 million Americans and claimed 675,000 lives as a result; a case-fatality rate of 2.3 percent. The Spanish Flu claimed greater numbers of young people than typically expected from other influenzas.
Beginning in January 2009, another H1N1 virus—known as the “swine flu”—spread around the globe and was first detected in the US in April of that year. The CDC identified an estimated 60.8 million cases and 12,469 deaths; a 0.021 percent case-fatality rate.
Notice the CDC uses the estimated number of cases and deaths to calculate and report these case-fatality rates. If the media wanted to honestly compare the case-fatality rates, they should use the estimated numbers to compute the case-fatality rates
IF we were to calculate the case-fatality rate for influenza only using confirmed infection cases found by testing and actual deaths from influenza, we would see an increase in the case-fatality rate.
So, let's look at a table showing the data so far.
I do not believe that comparing the case-fatality rate for MO to the estimated case-fatality for the entire United States allows someone to answer the question put forth in the article. So, let's look at the number of reported COVID 19 infections and deaths from COVID 19 as reported by the CDC on August 14. These are NOT estimates, these are confirmed total cases. Even the CDC is not incorporating their own belief about the estimated number of cases.
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