A new variant of SARS-CoV-2 in France seems undetectable by PCR

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A new variant of SARS-CoV-2 in France seems undetectable by PCR


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

The SARS-CoV-2 virus is the causative agent of the 2019 coronavirus disease pandemic (COVID-19) which continues to ravage the world 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 commune of Lannion in the Côtes d’Armor on the 13th.e Of March.

On Monday, the Department of Health said in a statement that initial analyzes for the variant did not suggest this new strain is more transmissible or causes more severe disease than previous viral strains.

However, at a press conference on Tuesday, health officials said there were concerns about the failure of PCR tests to detect the virus.

Belgian virologist and interfederal spokesperson for COVID-19 Steven Van Gucht said about eight people had typical symptoms of coronavirus, “but the tests remained negative”.

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


Crédit d’image: Hand Robot / Shutterstock

WHO classifies new strain as “variant under study”

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

The VUI category includes thousands of natural variants, of which only a small fraction is likely to pose a risk to public health.

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

However, as Gucht reminded people on Tuesday, new variants are expected to emerge as viruses constantly evolve mutations in their genome.

What about the tests?

Also, many different tests are used by different labs, and it is possible that a particular test could have problems detecting a certain variant, Gucht added.

“That doesn’t necessarily mean that’s the case for all other tests – quite the opposite,” he said.

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

“Usually, a good test doesn’t depend on detecting a 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, ”Gucht says.

The authorities implement the necessary monitoring and support

In the meantime, the French health authorities are implementing the necessary follow-up and support measures.

Public Health France and the national reference centers have set up a system for detecting and monitoring potential cases or carriers of the new VUI in areas such as Lannion, Guingamp, Saint-Brieuc and Morlaix.

The general directorate of health 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 the viral spread by accelerating vaccination and recalling the importance of protective measures such as social distancing and limitation the number of people at the gatherings.

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