What makes a variant a new strain? What makes a new disease, such as Covid-19 versus Covid-21? Well, much of it turns out to be semantics. What is supposed to classify a new strain is a significant change in a virus' behavior in relation to pathogenicity, immunogenicity, transmissibility, and/or virulence. So, is Omicron just another variant?
Let's look a little closer at its traits compared to previous variants in these critical areas:
1. Pathogenicity - there is convincing data that Omicron does indeed possess a dramatic change in pathogenicity. Multiple animal models evidence that Omicron infects the bronchi tissue much more efficiently (7000%), and infects the lung cells much less efficiently (-3000%) than Delta.
Omicron appears to not need or use the transmembrane protease, TMPRSS2 for Spike protein priming or cell membrane fusion. Another major divergence in pathogenicity is that Omicron no longer exhibits cell to cell fusion via syncytia. It exclusively infects via the ACE2 endocytosis pathway.
2. Immunogenicity - It's recently been shown that Omicron generates robust immunity against the prior VOC, Delta. However, t...
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