Covid-19 screening PCR tests also detect other coronaviruses such as those of “common colds”?


“Did you test positive for Coronavirus? For which Coronavirus? ”, It can be read in a publication that went viral on Facebook. In the text, the PCR tests – the swab tests – that have been carried out to detect SARS-CoV-2 are questioned, stating that “in the human body there may be more coronaviruses” and that these laboratory procedures “detect anyone of them ”, even those that cause“ common colds ”.

questioned PCR tests “data-title =” questioned PCR tests – Covid-19 screening PCR tests also detect other coronaviruses such as “common colds”? – Polygraph “> PCR tests questioned

The author of the post concludes that this is the reason for “so many false positives to appear” and guarantees that to confirm a positive result it is only necessary that there is a trace of one of the viruses in this family in the body. “Even if it is not recent because it detects viral remains”, he concludes.

Do these statements have any scientific basis? Verification of facts.

In statements to the Polygraph, Celso Cunha, virologist at the Institute of Hygiene and Tropical Medicine, explains that, although there are many PCR tests, those that are used to find “the genoma do SARS-CoV-2 were designed to detect it and are absolutely specific for this particular virus ”.

That is, the tests research the genetic material SARS-CoV-2, the new coronavirus that causes Covid-19, in the sample collected by zaragatoa and nothing else. In practice, these “are not able to detect the other seasonal coronaviruses, which cause common colds, under the conditions experimental that are used, let alone any other virus that belongs to a family different coronaviruses ”, stresses the expert.

Tests are also unable to identify portions of this genome, the “viral remains” that remain in the body “even if [a infeção] don’t be recent ”. “I must say that the genetic material outside the protection that give it the structural proteins of the virus is quite unstable and tends to degrade quickly. Therefore, the detection of these ‘remains’ is possible, but unlikely”, Concludes Celso Cunha.

The president of the National Association of Public Health Doctors (ANMSP), Ricardo Mexia, had also explained to the Polygraph that there is no possibility to be “diagnosing Covid-19 which was flu after all.” PCR tests “identify genetic material of the virus. It does not mean that among other viruses there cannot be a cross reaction, but tend to be tests very specific“, he stressed.

In late July, the Polygraph reviewed a publication claiming (falsely) that the margin of error for Covid-19 tests is greater than 80%. In fact, the sensitivity rate of the tests is high, even though it is impossible to guarantee success 100% results. Test defects, contamination or poor sampling can alter the results of the diagnostics. And none of these elements it is related to the original error margin of the test.

It can be concluded that it is false that the PCR tests designed to detect the new coronavirus give rise to many false positives, results that would be related to the fact that these laboratory tests allegedly also detect viruses responsible, for example, for seasonal flu.


Editorial note: this content was selected by the Polygraph in the scope of a partnership of fact-checking (fact check) with Facebook, designed to assess the veracity of the information circulating on that social network.

On the Facebook rating scale, this content is:

False: the main content claims are factually inaccurate; this option generally corresponds to the “False” or “Mostly False” classifications in sites fact-checkers.

On Polygraph evaluation scale, this content is:


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