Researchers warn of a new variant that is almost undetectable in PCR

A study by French researchers warns of a new variant that manages to go unnoticed in nasopharyngeal PCR

They define it as “poorly detected” and “with high lethality”: in an outbreak in France, only 15% of infected patients tested positive

Scientists only managed to isolate the virus in samples from the lower respiratory tract, in the lungs

The complex world of variants of the SARS-CoV-2 coronavirus continues to be talked about, although in this case, the variant in question -the French- it is not yet one of what experts call “worrisome”. The WHO classifies it, for the moment, as “variant under investigation”. Y what worries the most is that it is getting almost unnoticed in the virus detection tests.

A study by French researchers that has just been published shows that only 15% of the patients who had the B1616 variant, as it is called, tested positive in standard tests with nasopharyngeal swabs (PCR), compared to a detection rate of 97% for the other variants circulating in France. The study concludes that detection could be improved by going deeper into the lungs.

“Badly detected and with high lethality”

Scientists, researchers from the Saint-Brieuc Hospital Center, the Pasteur Institute and other hospitals and research centers, warn that what happened is important, because almost half of the patients infected with this variant died in less than a month. The rate is much higher than that of the rest of hospitalized patients with covid, whose mortality rate is 16%. Therefore, they warn of a new variant “poorly detected” and “with high lethality”.

Although the researchers also warn that this high mortality rate should be treated with caution, because Most of the patients who died after being infected with this variant were in their 80s.

The study says that at the beginning of January, the west of France registered an outbreak of an infectious disease, supposedly covid, which was what set off the alarms. Because the patients had typical covid symptoms, but the majority of the PCR tests were negative.

To the confusion of the doctors, all of them remained hospitalized in separate areas from the patients with covid. But investigators have managed to find out what was going on. They isolated a hitherto unknown variant of SARS-CoV-2. How? Taking samples of the virus in the deepest areas of the lungs.

PCR tests were “repeatedly negative in nasopharyngeal specimens but positive in samples from the lower respiratory tract “, they explain. That is the virus was lurking in the windpipe and lungs. Upon detection, “whole genome sequencing revealed a new variant.”

More elusive and less contagious variant

They explain in the study that the B1616 variant has nine mutations in its genome, and that includes the so-called E484K, known as “Erik” and present in the South African and Brazilian variants. This mutation is worrisome, because it has been seen that it allows the virus to elude, in a certain way, the immune response of the antibodies. Nevertheless, not the main concern of the B1616.

Researchers believe that her greatest skill is to go unnoticed. And that this may be because it would reduce the infection in the upper respiratory tract. They argue that some viral particles may remain in the nose or throat, but that their number would be “below the limit of detection” of commercial test kits.

And they have seen something else: that less viral shedding by coughing or sneezing would make it less contagious. Because when analyzing their spread, they saw that the outbreaks were limited to small groups. According to scientists To avoid detection, the virus could have sacrificed part of its transmission potential. And that, luckily for us, puts it in a worse situation when it comes to competing with other variants, such as the B117, which are much more transferable.

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