CDC has not said SARS-CoV-2 has never been isolated

29 September 2021
What was claimed

CDC document confirms that SARS-CoV-2 has never been isolated.

Our verdict

This is wrong. The document was talking about a process used to understand the ‘lower limit of detection’ during the creation of PCR tests. SARS-CoV-2 has been isolated many times.

An Instagram post shows a screenshot of a headline from the website Daily Expose, which describes Covid-19 as a “hoax” and states: “CDC documents admit they have never isolated the virus”.  

Isolating a virus means taking a pure sample of a virus from an infected being so it can be studied. As we have written before, there are numerous reports of the SARS-CoV-2 virus being isolated by teams around the world.

The Centers for Disease Control and Prevention (CDC) document that the post, and the Daily Expose article, refer to was published in July 2021 and includes “instructions for use” for PCR tests. 

One passage in this document states that no “quantified virus isolates” of the 2019-nCoV (the virus which causes Covid-19, also known as SARS-CoV-2) were available to the CDC for use at the time the PCR tests were developed. This is not the same as saying the virus has never been isolated, as claimed by the Instagram post.

In full, it says: “Since no quantified virus isolates of the 2019-nCoV were available for CDC use at the time the test was developed and this study conducted, assays designed for detection of the 2019-nCoV RNA were tested with characterized stocks of in vitro transcribed full length RNA (N gene; GenBank accession: MN908947.2) of known titer (RNA copies/µL) spiked into a diluent consisting of a suspension of human A549 cells and viral transport medium (VTM) to mimic clinical specimen.”

The meaning of this passage has been debated before, and has been used by some to suggest that SARS-CoV-2 has not been isolated. 

However, Dr Thushan de Silva, from the University of Sheffield’s Department of Infection, Immunity and Cardiovascular Disease, has previously told Reuters that this is not correct.

He explained that the document is outlining a “very common process” that is used to determine the lowest amount of viral genetic material the PCR tests could detect. To calculate this limit, he said:“You need to have a known quantity of virus to extract genetic material (RNA) from, or alternatively a known quantity of RNA identical to that carried by the virus”. In this case, the identical RNA that the CDC used was ‘transcribed’ RNA. This is synthetically produced genetic material which is identical to that carried by the virus, and, according to Dr Stephen Griffin, a virologist and Associate Professor at Leeds Institute of Medical Research, means that scientists already know how much genetic material is present in the sample. 

Dr De Silva explained to Reuters that at the time the tests were being created at the start of the pandemic, not many “standardised and quantified” viral stocks would have been available. These are stocks of the virus where the amount of viral RNA present is already known, and the way that it reacts in processing is understood. 

Dr Stephen Griffin told Full Fact that this is important to create a standard for the PCR test, so that other important features such as the efficiency of the PCR reaction or the impact of what solution the swab sample is put into can be understood and interpreted. 

He explained “you can't make it quantitative with a virus stock that's not been characterised. So you start with an in vitro [in the lab] transcribed RNA, it’s much better, it's easier to do that."

Using transcribed RNA rather than RNA extracted from quantified viral stocks is no reason to question the existence of SARS-CoV-2. Dr Griffin told Full Fact it is a “ standard technique”. 

Dr De Silva  told Reuters: “There are now hundreds of stocks of cultured SARS-CoV-2 in laboratories around the world”. 

Dr Griffin previously told Full Fact: “SARS-CoV2 has been sampled millions of times over from infected people, including those originally found to be infected in China,”.

The Instagram post is also accompanied by a caption which claims that Covid-19 is a “common cold”. 

We have written many times before about false claims that Covid-19 is the same as a common cold, is nothing more than a common cold, or a rebrand of flu.

The word ‘coronavirus’ has been used as a shorthand for SARS-CoV-2. But coronaviruses are actually a group of hundreds of different viruses, some of which cause severe diseases like Severe Acute Respiratory Syndrome (SARS) and Covid-19. Others cause much milder diseases, such as the common cold. This does not mean Covid-19 is the same as the common cold. 

This article is part of our work fact checking potentially false pictures, videos and stories on Facebook. You can read more about this—and find out how to report Facebook content—here. For the purposes of that scheme, we’ve rated this claim as false because the CDC document does not show that SARS-CoV-2 has never been isolated, and Covid-19 is not the same as the common cold.

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