New French COVID Variant Invisible to PCR Tests
French authorities have announced the detection of a variant of SARS-CoV-2 in the northwestern region of Brittany that has escaped detection by standard polymerase chain reaction (PCR) tests.
Real-time PCR tests are considered to be the current gold standard for detection of SARS-CoV-2, and currently take 4-6h to yield a result. PCR tests make millions to billions of copies of a small sample of DNA to create a larger sample for analysis.
Eight carriers of the variant were identified using genomic sequencing among a cluster of 79 cases in the town of Lannion in the Côtes d’Armor on March 13th.
In a statement on Monday, the French health ministry said that according to initial analyses, the new variant did not appear more transmissible or cause more severe disease. However, on Tuesday, authorities said that this variant was able to escape detection in PCR tests is raising concern.
Belgian virologist and interfederal COVID spokesperson Steven Van Gucht clarified the situation, in that about eight individuals presented with standard coronavirus symptoms, “but the tests remained negative.”
The World Health Organization has labelled this new French COVID variant a ‘variant under investigation’ (VUI), of which there are many thousands currently being monitored, as opposed to more serious variants like the South African B.1.351 variant which is more transmissible and is a ‘variant of concern’ (VOC).
However, just because this variant escaped the PCR tests being used in that area does not mean that it necessarily can escape all of them, as laboratories vary in the tests that they perform.
According to Gucht, tests differ in the different parts of the virus they look for, and also test for at least two to three. “Usually, a good test does not depend on detecting one specific part. So, if there is a mutation in one part of the virus, that signal may be lost, but there is usually a second or third signal that will be found,” explained Gucht.
French authorities are setting up systems to monitor the spread of this variant, and are also putting measures in place to contain it.
Source: News-Medical.Net
