Coronavirus variant found in France may escape PCR nasal smear tests

• France’s health ministry has identified a new variant of the coronavirus that may escape some tests.
• So far, this variant does not appear to be more deadly or more infectious than other strains.
• The variant shares some mutations with another variant found for the first time in California.
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A region of France has been besieged by a version of the coronavirus that can hide from standard tests.

The French Ministry of Health and Social Affairs announced on Monday that, out of a group of 79 cases of COVID-19 in Brittany, eight patients were infected with the new variant, but several of them had a negative result.

Despite these negative tests, patients had typical symptoms of COVID-19.

The new variant does not yet have an alphanumeric designation. But it is not the first variant that seems capable of escaping the tests. Finnish researchers announced last month that they identified a strain called Fin-796H with a mutation that made detection difficult with some nasal smear tests.

The inability to accurately diagnose infected people may make it more difficult to reduce the spread of the virus at a time when cases across Europe are already on the rise.

Confirming infections with the new variant is complicated

REUTERS / Gonzalo Fuentes

Standard molecular laboratory tests – known as reverse transcription polymerase chain reaction (RT-PCR) tests – look for an infection in a swab of a patient’s nose, looking for the coronavirus genetic code.

But, according to the French Health Directory, genetic sequencing revealed that the variant found in Brittany has several mutations in its spike protein that help prevent detection by these diagnostic tests.

Health officials in Brittany finally confirmed some of the cases caused by the new variant by testing patients’ blood for antibodies or by collecting samples of phlegm that patients coughed from inside their lungs and doing an RT-PCR test.

But none of these methods are typical COVID-19 tests, which suggests that the new variant may be circulating undetected in France and possibly beyond.

However, a European diagnostics company, Novacyt Group, announced Thursday that your PCR tests can successfully detect the new variant.

The variant does not appear to be more deadly or more infectious

THOMAS SAMSON / POOL / AFP via Getty Images

All eight French patients infected with the new variant died of the virus, according to the local LaDepeche agency, but local health officials said it does not necessarily mean that it is more deadly than other strains.

There is still no evidence that the strain is more transmissible than other versions of the virus. Further studies are still needed to find out whether it can prevent vaccines or antibodies from previous coronavirus infections, the French Ministry of Health said in a statement.

The genetic profile of the variant shows that it does not share any major mutations with B.1.351 and P.1 – the variants found for the first time in South Africa and Brazil, respectively – which are more contagious and may partially escape vaccines.

The Brittany variant is in the same group of strains as a variant found for the first time in Southern California. Variants in this group, called Clade 20C, are expected to account for a fifth of worldwide coronavirus infections by April, according to Nextstrain, a genetic repository that tracks coronavirus evolution over time.

Alain Jocard / AFP / Getty Images

The news of the variant in Brittany came amid the third peak of infections in France.

The average number of daily coronavirus cases has doubled since mid-December, jumping from less than 15,000 to an almost record high of more than 38,000 on Wednesday. The increase prompted Prime Minister Jean Castex to announce new blockades to Paris and the neighboring region of Ile-de-France on Thursday.

France is under a nationwide curfew between 6 pm and 6 am in the past two months.