Covid-19: the Breton variant, a strain with many unknowns

The first French variant ” under surveillance “ is Breton. The health authorities have confirmed that the same mutation of SARS-CoV-2 had been found in eight patients who died at Lannion hospital, in a cluster of 79 cases identified since February in the Côtes-d hospital. ‘Armor.

→ THE FACTS. Detection of a Breton variant of Covid-19

Any “Causality” between this variant and deaths is currently “Established”, repeated on March 16 Stéphane Mulliez, director of the Regional Health Agency (ARS) Bretagne, describing people “Old enough” suffering from “Significant comorbid factors”. But the specificities of this new strain require investigations.

Its peculiarity is firstly its low detectability by nasopharyngeal examinations. Seven of its first eight carriers were negative on the classic PCR test. The doubts of health workers about their “Typical symptoms of Covid-19” then new samples, serological or deeper respiratory, confirmed the presence of SARS-CoV-2, in an unprecedented form revealed by sequencing.

“The first variant to defeat the PCR test”

“This variant would be the first in the world to defeat the test most used to diagnose Covid-19”, describes Pierre Tattevin, head of the infectious diseases department at Rennes University Hospital. A “Originality” which prevents, as it stands, to conclude on its lethality from the only deaths observed. “Mild cases risk being invisible by negative PCR tests if they are not followed by deep samples from the lungs ”, explains the infectious disease specialist.

The reasons for the resistance of the variant to the swab are only hypotheses today. Virologist at Rennes University Hospital and among the first to have sequenced it, alongside the National Reference Center (CNR) Pasteur, Vincent Thibault notes that“It is found in any case very little in the upper airways” : “Either the virus descends more quickly at the pulmonary level. Either it replicates very little in the upper airways and only becomes pathogenic once it has arrived in the bronchi, where it is detected. “

Contagiousness, severity, possible immune escape of the variant, which would make it resistant to vaccination or to a first infection: faced with all these unknowns, the health authorities have ordered several “Investigations”.

A less contagious mutation?

In Côtes-d’Armor and Finistère, the Directorate General for Health (DGS) has revised its “Definition” cases “Possible” and “Probable” infection with Covid-19 to encourage in-depth diagnoses at the slightest suspicion and increase sequencing. “We will do nasopharyngeal tests and, when possible, look for the virus elsewhere in the body (lower respiratory system) to increase the sensitivity of our analyzes, details Sibylle Bernard-Stoecklin, epidemiologist at the infectious diseases department of Public Health France (SPF). The goal is to miss as few cases as possible, to limit its spread and to clinically document this variant. “

A new “flash survey” was also organized on March 16 to refine the prevalence of this strain among patients. “For Brittany, we will be exhaustive”, announces Sibylle Bernard-Stoecklin: “All positive samples for SARS-CoV-2 which will have been detected that day in a Breton laboratory will be transmitted to a sequencing platform. “ The results are not expected until next week. “But based on preliminary information, we have no evidence for an increased transmissibility or severity of infection caused by this variant.”, insists the epidemiologist.

→ EXPLANATION. Covid-19: Are the new variants worrying?

And if his “Originality” made it less transmissible? “It is possible that patients are less contagious without this phase of carrying in the nose, which is still the main means of dissemination of the virus”, advance Pierre Tattevin. It is one of the unknowns to be overcome in the Côtes-d’Armor, which displays an incidence rate almost half lower than the average for the country.


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