Omicron didnt evolve from.Beta or Delta

Interesting one from Dr Campbell tonight ( link below and I looked over papers also).

In summary he presented the following.

Omicron didnt evolve from Delta or Beta.  It split off  from the original Wuhan strain around mid 2020.  It then disappeared for 18months.

 During this time it accumulated mutations at a  much faster rate than normal ( 1.5 mutations a month instead of usual 0.5 mutations indicating it was under strong selective pressure.

So ..where did it go for 18 months and what allowed its mutation rate to be so high ?

3 interesting theories but evidence points to 3rd theory.

1) It was circulating and mutating in a population which had no PCR testing, so was undetected but was infecting people and changing.  ( this however doesnt explain it's unusual high mutation rate)

2) It was in a chronically infected individual where it quietly gathered mutations.  For example a human with HIV cant clear the virus, it lives and divides and mutates  in that person continuously.  The person acts as an incubator.  This though still doesnt explain its high mutation rate. 

3)  In mid 2020 omicron predecessor left the human population and jumped into mice.  There it  underwent a faster mutation rate ( common in animals), the mutations were especially within the spike protein and  it is shown to have adapted to fit the slightly different  Mice ACE2 receptors perfectly.  18 months later  It  jumped back to humans.  Mice ACE2 receptors are more like our upper airways and not like our lower airways.  This meant the mutated virus now adapted to mice,  could accumulate in huge numbers in humans upper but not lower airways.  Here it is  close to the point of exit ( nose and mouth) so could be more infectious than Beta or Delta.  Also avoiding the lower airways could be less pathogenic.

So Dr Campbell finishes by saying....was it just luck that 

1) Omicron escapes vaccine, out competes pathogenic delta, and  infect and immunised us without causing severe disease.( data not complete yet but so far in Scotland indications are it is less  severe). ( also unknown if omicron can prevent reinfection with delta)

2) Are we also lucky that it was mice it jumped into and not another animal like camel.  Camels Ace2 receptors are like our lower airways.   So it could have emerged adapted  to more efficiently infect our lower airways and cause a MERS like illness which is 35%CFR.  ( lower airways is also closer to blood so becomes a blood virus as well as a lower respiratory.)

Anyway I found it interesting.  Must start telling my cats  "Mice are Nice"  and to stop drowning them.  My cats hold them under the water with their paws... it's a trait of their breed...crazy cats.

Hz x

https://youtu.be/aH1u1GIPU2A