Why Omicron quickly became a variant of concern
The WHO lets Omicron skip over variant of interest, go straight to concern.
THAT'S A LOT OF MUTATIONS!
". . .Many changes
While the Delta variant's version of spike has nine changes compared to the virus that started the pandemic, Omicron has 30 differences. While many of these haven't been identified previously, a number of these have been seen in other strains, where they have a variety of effects. These include increasing infectiousness of the virus, as a number of the changes increase the affinity between the spike protein and the protein on human cells that it targets when starting a new infection.
Other changes in the spike occur in areas of the protein that are frequently targeted by antibodies that neutralize the virus. Changes here can mean that an immune response generated to vaccines or earlier versions of the virus are less able to target Omicron.
While these mutations are suggestive, understanding how they and the previously undescribed mutations in Omicron alter its behavior will depend on getting real-world data on its spread. Right now, however, we just don't have much of that.
We are lucky in the sense that it's relatively easy to detect Omicron. According to the WHO, some of the large collection of mutations in the gene that encodes the spike protein interfere with the gene's recognition by common versions of PCR tests. Those tests continue to recognize the presence of the virus by also targeting other areas of the genome. So a PCR test that comes back spike-negative but virus-positive is suggestive of the presence of Omicron, which can then be confirmed by genome sequencing.
These tests have shown Omicron is spreading rapidly within a number of countries in Southern Africa, although the total cases in Botswana and South Africa remain relatively low at the moment, so the significance of this spread is unclear. . .
READ MORE: https://arstechnica.com/science/2021/11/why-omicron-quickly-became-a-variant-of-concern/
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