Thread by @sailorrooscout

Good morning! I hope everyone had a wonderful holiday yesterday. ☃️🎁🎄

Currently working on a thread that’s shows while Omicron is more transmissible than Delta, it is LESS fusogenic and LESS pathogenic than both Delta AND ancestral SARS-CoV-2 if it is of any interest.

A study out of the University of Tokyo shows while Omicron is more transmissible than Delta, it is LESS fusogenic and LESS pathogenic than both Delta and ancestral SARS-CoV-2. In addition, Omicron infection in the lung is significantly LOWER.

Let’s talk about that and more!🧵

Source for the information above can be found here:
•drive.google.com/file/d/1rhCazF…
•nature.com/articles/s4158…
For definitions and some general background reading I recommend:
•pubmed.ncbi.nlm.nih.gov/33348900/

In contrast to Delta, Omicron is LESS fusogenic (left) and its spike is faintly cleaved (right). Why does this matter? Because research suggests the efficiency of spike protein cleavage, fusogenicity and pathogenicity correlate with one another.

Their statistical analysis showed that Omicron is >3.0-fold and >5.6-fold more transmissible than Delta in South Africa and the UK, respectively.

In their Syrian hamster model, compared to Delta and ancestral SARS-CoV-2, Omicron poorly infected and spread in the lung and was less pathogenic. This data suggests that the efficacy of SARS-CoV-2 S cleavage and viral fusogenicity are closely associated with viral pathogenicity,

and Omicron has evolved to exhibit increased transmissibility and attenuated pathogenicity. Before you ask why Syrian Hamsters, their immune responses to infectious pathogens are similar to us, and as such, this animal model is advantageous for studying pathogenesis of infection.

This data does support findings from other labs as well discussed here in this thread.

https://twitter.com/sailorrooscout/status/1471100513353613314?s=21

Summary:
•Omicron POORLY infects and spreads in the lung
•Evolved to exhibit increased transmissibility and attenuated pathogenicity
•Both in vitro data and epidemiological data agree with some degree of decreased severity in regards to Omicron

•Data show that the pathogenicity of Omicron is attenuated compared to Delta and even its ancestor
•Data show that SARS-CoV-2 can evolve to attenuate its pathogenicity, because Omicron is phylogenetically classified as a B.1.1 descendant lineage
•Make sure you are PROTECTED

As I have said MANY times before. It is IMPORTANT to note severity of disease in humans is NOT determined only by virus replication but also by the host immune response to the infection. Make sure you are PROTECTED. DON’T WALK AROUND IMMUNE NAIVE.

The last thing I’ll add to this thread since there was some concern last week. Israel is now delaying rollout of their 4th COVID dose amid signs Omicron seems to be less severe amongst those who are not immune naive. So make sure you are protected.
timesofisrael.com/israel-said-to…