New SARS-CoV-2 variant in France appears undetectable by PCR

French authorities have announced the emergence of a new variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in the northwestern region of Brittany that has escaped detection by standard polymerase chain reaction (PCR) tests.

The SARS-CoV-2 virus is the agent responsible for the coronavirus disease 2019 (COVID-19) pandemic that continues to ravage the globe and has now caused more than 2.67 million deaths.

An in-depth investigation is now underway in Brittany after genomic sequencing identified eight carriers of the variant among a cluster of 79 cases in the town of Lannion in the Côtes d'Armor on the 13^th of March.

On Monday, the health ministry said in a statement that initial analyses of the variant do not suggest that this new strain is more transmissible or causes more severe disease than previous viral strains.

However, in a press conference on Tuesday, health officials said the failure of PCR tests to detect the virus is raising concerns.

Belgian virologist and interfederal COVID-19 spokesperson Steven Van Gucht clarified that about eight individuals presented with typical coronavirus symptoms, "but the tests remained negative."

The announcement comes as France sees a resurgence in SARS-CoV-2 cases, with President Emmanuel Macron warning that new lockdown measures could be implemented in the days to come.

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WHO categorizes new strain as "variant under investigation"

The World Health Organization (WHO) has categorized the new strain as a "variant under investigation" (VUI) rather than a "variant of concern" (VOC) like the strains that were recently identified in Brazil, the UK and South Africa.

The VUI category includes thousands of naturally occurring variants, of which only a small fraction are likely to pose any risk to public health.

Investigations are currently underway to better understand the variant and its response to the protective antibodies generated following previous SARS-CoV-2 infection or vaccination against the virus.

However, as Gucht reminded people on Tuesday, it is expected that new variants will emerge as viruses constantly evolve mutations in their genome.

What about the testing?

Furthermore, many different tests are used by different laboratories, and it is possible that a particular test may have problems detecting a certain variant, added Gucht.

"That does not necessarily mean that this is the case for all other tests – quite the contrary," he said.

Each test detects one to three different parts of the virus and different tests can detect different parts.

"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," said Gucht.

Authorities are implementing the necessary monitoring and support

In the meantime, French health authorities are implementing the necessary monitoring and support measures.

Public Health France and the National Reference Centers has set up a system for detecting and monitoring potential cases or carriers of the new VUI across areas including Lannion, Guingamp, Saint-Brieuc and Morlaix.

The general health directorate has also alerted health establishments and health professionals that the variant is being monitored.

Finally, as a precautionary measure, local authorities, prefectures and the Regional Health Agency are stepping up measures to mitigate viral spread by speeding up vaccination and reminding people about the importance of protective measures such as social distancing and restricting the number of people at gatherings.

Written by

Sally Robertson

Sally first developed an interest in medical communications when she took on the role of Journal Development Editor for BioMed Central (BMC), after having graduated with a degree in biomedical science from Greenwich University.