Detailed assessment of the new UK #SARSCoV2 variant by @WHO scientific team: https://www.who.int/csr/don/21-december-2020-sars-cov2-variant-united-kingdom/en/
Key points in thread.

2/ The @WHO takes a global view:
"One of the mutations identified (N501Y) is altering an amino acid w/in the 6 key residues in the receptor binding domain...same mutation independently reported in several countries including South Africa & Australia...originated separately."
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3/ This means that under selection pressure, as far apart as Cape Town, Sydney and London, #SARSCoV2 is forming mutations in the identical region of the spike protein that binds to human cells, and against which we make antibodies.
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4/ In addition, "Another mutation of biological significance, P681H, has been found in the," binding region of the spike protein. Evolution seems to favor forms of the #COVID19 virus that can evade the immune system and/or more efficiently infect human cells. @WHO
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4/ These mutations may hamper diagnostic testing because, "the deletion at position 69/70 has been found to affect the performance of some PCR assays that use an S gene target." Fortunately, most #COVID19 infection tests look for a broader range of #SARSCoV2 targets.
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5/ How will this impact the #COVID19 #vaccines? @WHO says, "Laboratory studies are ongoing...There is not enough information at present to determine if this variant is associated with any change in severity of clinical disease, antibody response or vaccine efficacy."

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6/ These possibly dangerous mutated forms of #SARSCoV2 were discovered, says @WHO, because "On average, between 5 - 10% of all SARS-CoV-2 viruses have routinely been sequenced in the UK."
Nothing akin to this is done in the United States. We have no such govt surveys in USA.
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7/ Says @WHO of the UK mutant: "Most #COVID19 cases from whom this variant has been identified have occurred in people under 60 years of age."
The same is true of the South African mutant, which is hitting <40-yr-olds especially hard & causing worse disease, says SA govt.
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8/ @WHO notes of UK mutant, "this variant is more transmissible than previous circulating viruses, with an estimated increase of between 40% & 70% in transmissibility," bring the Ro up to 1.7. This explains the explosion of #COVID19 cases in UK now.
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9/ So, says @WHO, all viruses mutate. That's normal.
But, "Further epidemiological & laboratory-based studies are rapidly required to understand the implications of these viruses in terms of available #SARSCoV2 clinical presentation, diagnosis, treatment & vaccine development."